  Q. What is an angle? A. An angle is the divergence of two intersecting lines. Fig. 57. In Fig. 57 the two intersecting lines SA and XA form the angle SAX, and when measured on the circle with A as the center it is found to be equal to 80°.45 (eighty and forty-five hundredths degrees). Q. Into how many degrees is a circle divided? A. 360. Q. How is each degree divided in the U. S. Artillery service? A. Each degree is divided into one hundred equal parts. Q. Define a circle. A. A circle is a plane figure bounded by a curve, every point of which is equally distant from a point within called the center. Fig. 57 represents a circle with A as the center. Q. What is the vertex of an angle? A. The point where the two intersecting lines cross. As in Fig. 57, A is the vertex of the angle SAX. Q. Define an azimuth angle. A. It is a horizontal angle measured from zero degrees at the south in a clockwise direction. Q. What is meant by a horizontal angle? A. One whose intersecting lines or sides are parallel with the level of water at that point. Q. What is a vertical angle? A. One whose sides lie in a plane of a plummet. Q. Can an azimuth angle be greater than 90°? A. Yes. See Fig. 51. SAT = azimuth of target (less than 90°); SAT' = azimuth of target (greater than 90°, but less than 180°); SAT'' = azimuth of target (greater than 270°). (All these azimuth angles are read in a clockwise direction from zero at the south.) Q. When is a gun or an instrument said to be set in azimuth? A. When it reads zero and points south. Q. What is an azimuth-instrument? A. A device for measuring horizontal angles. Q. Point out the following parts of the instrument:
A. See Fig. 58. Q. Describe how to set the azimuth-instrument up for use. A. First: Set the graduated circle and index-disc to read the known azimuth of a visible object and clamp (the eccentric-crank being in gear). Second: Set the eyepiece slightly to the left of the reading-opening and tighten the azimuth-clamp. Third: Raise the whole instrument by grasping the tripod, and turn it so that the telescope points approximately in the direction of the visible object whose azimuth is known, being careful to set the plumb-bob over the home station at the same time and not destroy the setting of the graduated circle and index-disc. Fourth: Level the instrument. (This is done by loosening the azimuth-clamp and setting one level parallel to two opposite leveling-screws, then turn these two screws either both inward toward the spindle-head or both outward until the bubble comes in the middle. Perform the like operation with the other two leveling-screws and the instrument is level.) Fifth: Release the azimuth-clamp and set the telescope as nearly as possible on the object, then clamp and set the vertical cross-hair exactly by turning the azimuth slow-motion screw. Verify the setting of the index-disc and the levels. The instrument is now set in azimuth. Azimuth instruments for mounting on the parapet have turned on their levelling screws so as to bring reading opening convenient to the eye. Q. How is the azimuth of any other point read after the instrument is set up? A. By turning the index-disc crank until the vertical hair cuts the object. Read the even degrees on the graduated circle, and hundredths of a degree on the index-disc. (In order to make a considerable change in azimuth-reading, much time is saved by releasing the eccentric-crank, turning the telescope approximately on the object, throwing the eccentric-gear again and reading Q. Why are not azimuth-circles on guns, mortars, etc., always graduated so that their zeros will point south? Fig. 58. A. If this were always done, the azimuth indicator-plate or subscale would have to be directly under the muzzle of the gun—a very awkward and inconvenient place. These azimuth sub-scales are therefore placed on the side, and when the gun or mortar points south the subscale points at zero on the azimuth-circle. Q. Give some rules for caring for the azimuth instrument. A. Never allow any of the leveling-screws to become so tight that they cannot be easily turned by hand. When setting the instrument up over a concrete floor make little holes in the concrete Q. In case the azimuth-instrument will not stay level after performing the usual operation of leveling, how do you adjust the levels? A. Set one level parallel with two opposite leveling-screws, and bring the bubble to the center by turning these two screws either both inward or both outward. Reverse the telescope through 180°. If the bubble is not in the center, this level is out of adjustment. Now correct one half of the error by using the small steel pin on the little adjusting-screws on the levels, and the other half by using the two opposite leveling-screws referred to above. Now turn the telescope 180° again. If it is still out of level, continue the above method of correction until, on reversing the telescope, no change in motion of the bubble can be observed. Q. Give a rule for finding the least count of a vernier. A. Divide the value of the smallest division on the limb or main scale by the number of divisions there are on the vernier. The result is equal to the least count on the vernier. Q. How would you focus the telescope. A. Focus the eyepiece until the cross-wires appear rough. Then turn the telescope on some distant object and focus the objective by means of the focusing-knob until the intersection of the cross-wires remains on the same point, when the eye is moved up and down and to right and left. Q. Set up the azimuth instrument over a given point; level, orient, and focus it. (This should be practiced frequently.) Examples.—I. The number of divisions on a vernier = 25. The value of the smallest division on the main scale = 25 yards. What is the least reading of the vernier? Ans. 25 ÷ 25 = 1 yard. II. The value of the smallest division on the main scale of the mercurial barometer = 1/10 of an inch. The number of divisions on the vernier = 10. What is the least count of the vernier? Ans. 1/10 ÷ 10 = 1/100 of an inch. Note.—The following scheme for accurately counting seconds has been found valuable to gunners who have no stop-watches; it is also used by many photographers in timing pictures. When ready to start to count the time of flight, for example, trail your gun or instrument on the target, stop traversing, and count to yourself: One one thousand, two one thousand, three one thousand, four one thousand, etc., until finished, saying one thousand after each number. The time required by the average man to say one one thousand or eight one thousand is equal to one second. With but little practice a gunner can be trained to count as high as 20 seconds accurately. In such cases stop-watches are not necessary. (b) THE PLOTTING-ROOM.Q. Point out or describe the following parts of the Whistler-Hearn plotting-board: The table, the azimuth-circle, azimuth graduations for primary and secondary stations, base-line arm, base-line plate, primary station, secondary station, primary arm, secondary arm, directing-gun arm, directing-gun azimuth-circle, base-line verniers, directing-gun vernier, base-line-arm verniers, azimuth-indices for primary and secondary stations, auxiliary arm, connecting-bar, clamp for arm index-clamp, gun-arm clamp, reading-opening for directing-gun azimuth-circle, index for gun azimuth-circle, speed-scale for range, speed-scale for azimuth or azimuth-travel devices, range correction-device, azimuth correction-device, micrometer, the "targ, tally dials." A. See Figs. 59, 60, 61, and 62. These figures show by steps the "evolution of the Plotting Board." SIMPLE PLOTTING-BOARD. Fig. 59. PLOTTING-BOARD WITH GUN-ARM. Fig. 60. Q. Describe how to obtain the range of a target from the primary or secondary station when the azimuth-angles from the primary and secondary stations are given to you. A. First: Set the auxiliary-arm index to read the number of even degrees the target is from the secondary station, setting the arm-clamp in the V-shaped notch on the azimuth-circle corresponding to that number of degrees. THE MODERN PLOTTING-BOARD. Fig. 61. Second: Set the index-disc to read the hundredths by turning the index-knob and clamp the index. The auxiliary arm is now set; therefore the secondary arm is set automatically in azimuth by virtue of its always remaining parallel to the auxiliary arm. Third: Set the primary arm to read the number of degrees and hundredths the target is from the primary station. (The point of intersection of the fiducial or bevel edges of the primary and secondary arms is the position of the target on the plotting-board.) Fourth: Slide the metal intersection-block or "targ" along the secondary arm until it touches the edge of the primary. The range in yards can now be readily read on the scales marked on these arms. (Fig. 62.) WHISTLER-HEARN PLOTTING-BOARD. (Perspective Drawing. Secondary and auxiliary arms should be parallel.) Fig. 62. Q. How are the range and azimuth for the directing-gun obtained for the same target? A. Move the gun-arm up to the intersecting edge of the targ, and read the range from the scale on the gun-arm. The degrees of azimuth are read through the reading-opening, and the hundredths are read on the index-disc for the gun-arm. Q. Suppose the range must be corrected for, say, 150 yards more, and the azimuth for 1·78 degrees less, how can the corrected range and corrected azimuth be automatically read on the gun-arm? A. Turn the pinion on the gun-arm to move the scale of the range correction-device until 2150 is set. (The zero of this scale = 2000.) (By doing this it is readily seen that the gun-arm range-scale is just 150 yards nearer the gun center; consequently all ranges read on this scale will be 150 yards more than if the range correction-device were at zero.) The azimuth correction is set by turning the micrometer until the number of even degrees of the azimuth correction (in this case one degree less) is read on the main scale, and the hundredths on the micrometer. (Thus it is seen that the gun-arm will read as many degrees and hundredths more or less than the true azimuth as the number of degrees and hundredths of the azimuth correction determined.) Note.—Having determined by the ballistic board the range and azimuth corrections, they will usually answer for some time and thus avoid continual setting of these corrections on the gun-arm. Q. What is the object of the travel-devices for range and azimuth correction on the gun-arm? A. These are to determine the amount of change of range and azimuth between each observation of the target. The results thus obtained are given to the range- and deflection-board operators, who use it in finding the total range correction and the total azimuth correction. Q. What are all plotting-boards principally used for? A. For finding the position of a target whereby the range and the azimuth of it from any other point (as a directing-gun of a battery) can be determined. Q. What is meant by the scale of a plotting-board? A. By the scale of a plotting-board is meant, one inch on the board is equal to one, two, or so many yards on the ground; e.g., a scale of "one inch equals 300 yards" means, one inch distance on the board equals 300 yards on the ground. Q. How can you determine the distance between two points on a plotting-board? A. By using the range-arm that is constructed for the scale to which the board is drawn, setting the zero on one point and reading the number of yards on the arm where the point cuts the scale-edge. Q. How is the longitudinal deviation measured on the plotting-board? A. Measure the distance from the gun to the target, and from the gun to the splash. Subtract the lesser from the greater, and this will be the longitudinal deviation, according to the meaning given in drill regulations. Q. How is the lateral deviation measured? A. Read the azimuth of the target and splash from the directing-gun. Subtract the lesser from the greater: result = lateral deviation. If the azimuth to the target be greater than that to the splash, it is seen that the deviation will be to the left and vice versa. Q. How are open sights on rapid-fire guns used? A. The same as on small-arm pieces; i.e., the range in yards or elevation in degrees and minutes is set on the rear sight according to how the sight is graduated, and the gun is elevated and traversed until the target, front sight, and rear sight all come in line. Q. Describe the 5" R.F. sight. A. It consists of a sight-bar graduated in degrees and minutes (lowest reading being six minutes), with a sliding scale at the top for deflection right or left, the deflection-scale reading to three minutes. A range-drum is also geared to the sight-bar, and moves with it in such a manner that when the piece has a certain elevation it will shoot to a distance equal to the range on the drum. This avoids using any range-table. Q. Describe the 6-pdr. R.F. sight. A. A simple bar-sight graduated to yards with a deflection-scale reading to three minutes. Q. How is the deflection-scale set on open sights when it is desired to fire to right or left? A. To fire right, move the peep-hole to the right; to fire left, move the peep-hole to the left. Q. From what line is all elevation measured? A. From the axis of the bore. (See Fig. 63.) Fig. 63. Q. Define sight elevation. A. The angle between the axis of the bore before firing and the line of sight. (See Figs. 63 and 64.) Q. In case shot strikes to the right or left, and as gunner you had the sight on the target when the shot struck, how could you correct your error with a telescopic sight or open sights? A. Stopping traversing at the instant shot strikes, move the vertical hair rapidly to the splash. The sight is now corrected for the error, and its setting will be correct for the next shot. The Range-board.NOMENCLATURE. (See Fig. 65.)The Frame.—The outside frame, or box, of the instrument. The Board.—That upon which the charts are pasted. K-K. SIGHT SET FOR "QUADRANT ELEVATION" SIGHT SET FOR "SIGHT ELEVATION" (EXAGGERATED DIAGRAMS.) Fig. 64. The Ruler.—The balance wooden strip to which the metal scale and slides are attached. X-X. The Scale.—The fixed graduated scale on the ruler. m-m. The Bar.—The metal rod or bar which slides on the top of the scale. The Register.—The fixed point in the center of the bar. a. The Trammel.—The pointer which slides on the bar. b. The Pointer.—The pointer at the top of the trammel. The Index.—The lower point on the trammel. Normals.—The straight vertical lines in each set of curves. The String.—The cord on the right side of the board used in determining travel. The Travel-scale.—Scales for setting the string. Prediction-scale.—Vertical lines on the right side of the board, used in determining the travel during the observing interval. ADJUSTMENT.Adjust the ruler by means of the adjusting-screw on the left, so that its upper edge coincides with the parallel lines on the board. OPERATION.The bar is clamped by means of the screw near the left end of the ruler. The bar must be held firmly while moving the trammel. In making corrections for artillery fire the following data, as obtained at the opening of the action, will usually suffice for the entire action.
The range effects and deviating effects of the wind must be obtained for each shot. Tide should be changed at least every half-hour. As soon as the density of the air is ascertained the computer will insert a pin, or set the pointer at the top of the corresponding curve. The same will be done for height of tide. The muzzle velocity to be used for the first shot will be marked in a similar manner as directed by the range officer. The wind-component device having been set for the azimuth and velocity of the wind and the azimuth of the target, the computer will note the reference-number and set the pointer at the top of the wind-curve having that number. THE RANGE-BOARD. Fig. 65. As soon as he receives the travel reference-number he will set the string accordingly, using the scale for the observing interval used. To determine correction.—As soon as the approximate range is received, the computer sets the ruler for the range and the index at zero; he then slides the trammel to the left until the pointer is opposite the atmosphere curve as indicated by the pointers e, f, g, etc., holding the bar in place with the left hand. He then slides the bar until the pointer is at normal for atmosphere; this completes the correction for atmosphere. He then proceeds in the same manner for wind and tide, always sliding the trammel until the pointer is at the indicated curve, holding the bar in place with the left hand and then sliding the bar until the pointer is at normal. If the muzzle velocity is normal, no correction is made for velocity. If, however, the muzzle velocity is not normal, he makes a correction for muzzle velocity in a similar manner as for other data. The above corrections are made before the travel is received. The computer clamps the bar and then waits until he receives the travel. As soon as the travel is received, he sets the string, slides trammel until the pointer is opposite the string, unclamps the bar and moves it until the pointer is opposite the normal; this adds the correction for travel during the time of flight. He then notes the total travel during the observing interval, which is indicated by the position of the string on the travel-scale corresponding to the observing interval used. He slides the trammel so that the pointer will be at the vertical line corresponding to the total travel during the observing interval, and then slides the bar to the normal; this adds the travel during the observing interval. He now clamps the bar. The register now indicates the total correction to be applied to the arm. Trial-shots.—The gun is laid so that the shot should have a certain range, all corrections having been determined as described above, except of course that for travel. The bar is set with the index at zero, and the trammel is set at the muzzle velocity used in the computation for the shot. The gun is fired and the range of the shot is plotted. The range officer determines how much the shot has fallen short or gone beyond, and announces the result as plus or minus so many yards. The computer moves the bar plus or minus the number of yards announced, using the scale for this purpose. The pointer now indicates the muzzle velocity to be used in computing the next shot. The velocity pointer is moved accordingly. If a second trial shot is used, the corrections are computed as before, using, however, the new muzzle velocity as determined from the first shot. In determining a second corrected muzzle velocity the bar should be moved for but half the longitudinal deviation of the shot from the expected range; the pointer then marks the velocity to be used for the next shot. In case a third trial shot is used the process is the same except that the bar is moved for but one third of the longitudinal deviation. The curves are given for every ten yards of range, for every ten per cent of weight of air, and for every ten miles of wind, etc. For conditions in which the values lie between these readings, the trammel can readily be set by the eye sufficiently close for all practical purposes. Example: Range 7000; atmosphere 20; wind 70; velocity 2260; travel 400; tide +10. Find the correction to be applied to the gun-arm. Solution:
The Deflection-board.NOMENCLATURE.Platen.—The rectangular sliding frame. Wind-arm.—The arm pivoted to the board on the left of the platen. Wind-component Scale.—The scale above the movable end of the wind-arm. Drift-curve.—The curved edge of the metal plate attached to the left end of the platen. Travel-arm.—The arm pivoted on the platen. Azimuth Correction-scale.—The sliding scale below the platen. Deflection-scale.—The fixed scale immediately above the azimuth correction-scale. THE DEFLECTION-BOARD Fig. 66. Travel-scale.—A scale for making corrections for angular travel of the target; there are two, one below the azimuth correction-scale and one on the platen. "T" Square.—The sliding "T" square having the time graduations at one edge, corresponding to given ranges. OPERATION.Place the travel-scale on the platen in the lower or upper position according as the observing interval is 10 or 20 seconds. As soon as the wind-component device is set note the deflection reference-number indicated, and set the wind-arm to the corresponding reading on the wind-component scale. Set the platen so that the point of the drift-curve corresponding to the given range will be accurately over the right-hand edge of the wind-arm. As soon as the reference-number indicating the angular travel of the target during the observing interval is announced, set the travel-arm (right edge) for that travel by the travel-scale on the platen and set the azimuth correction-scale for the same travel by means of the travel-scale below it. Set the "T" square so that the point of its scale corresponding to the given range will be accurately over the right edge of the travel-arm. The azimuth correction to be applied to the gun-arm in all cases is then read from the azimuth correction scale at the bevel edge of the "T" square. When Case I or II is being used the deflection to be sent to the guns is read from the deflection-scale at the bevel edge of the "T" square. After the second observation the corrected range determined is used in setting the platen and "T" square. See Fig. 60. Q. How do the divisions on the azimuth-subscale and the deflection-scale of the sights compare with one another? A. They are equal—the least reading on the former = 5 hundredths, and on the sight-scale one point or division = 5 hundredths or 3 minutes. Q. How are the predicted range and predicted azimuth obtained? A. It is now, under the new system of fire direction, obtained by means of the travel correction on the range correction and azimuth correction-board. If these new boards are not yet issued, the use of a range-keeper's range prediction-scale and a gunner's azimuth prediction-scale determines them at the gun. The old method was by plotting several positions of a target on the plotting-board and using a prediction-ruler, whence the predicted point was obtained. Q. Define quadrant elevation. A. The angle between the axis of the bore before firing and the horizontal plane. (See Figs. 63 and 64.) Q. What is the difference between quadrant and sight elevation? A. Where the gun is above the target, sight elevation equals quadrant elevation plus the angular depression of the target. Where the gun is below the target, sight elevation equals quadrant elevation minus the angular elevation of the target. Q. How is the gunner's quadrant used? A. It is used principally in giving elevation to mortars by first setting the movable arm such that the knife-edged tooth engages in an even-degree mark on the rack, and by moving the sliding level to read the exact number of minutes. Then it is placed on its seat at the breech, being careful to see that the arrow points in the direction of the line of fire, and by elevating or depressing the piece until the bubble comes in the middle the mortar or piece will be set at the elevation set on the quadrant. (See Fig. 67.) THE GUNNER'S QUADRANT. Fig. 67. Q. Point out the following parts of the telescopic sight: Telescope, objective, eyepiece, erecting-prisms, trunnions, leveling-lug, leveling-screw, cross-level, elevation-arc, elevating-screw, vernier, focusing-collar, deflection-screw, deflection-scale, micrometer, disc, and telescope-level. (See Fig. 68.) THE TELESCOPIC SIGHT MODEL 1898. Fig. 68. Q. How is deflection set on it? A. By moving the deflection-screw the vertical cross-wire moves. Q. How is deflection set to fire right and to fire left? A. Move the vertical hair to the right to fire left, move it to the left to fire right, by turning the deflection-screw. Q. How is elevation set on it? A. Set the zero of the vernier opposite the mark on the limb representing the number of even degrees of the given elevation. Then turn the micrometer-disc by turning the elevation-screw until the given number of minutes is read on it. The sight is then set on the trunnion-bracket and the piece elevated till the bubble comes in the middle for quadrant elevation or till the horizontal cross-hair cuts the water line of target for sight elevation. The gun then has the elevation set on the sight. Q. What is the lowest reading of the vernier on the elevation-arc? A. Two minutes. Q. What is the lowest reading of the deflection-scale? A. Three minutes. Q. Why is it necessary to elevate the gun till the bubble on the telescope-level comes in the middle, to set the gun for quadrant elevation? A. Because by definition quadrant elevation is the angle between the axis of the bore and the horizontal plane, and when the bubble is in the center of the level the telescope is horizontal and the axis of the gun makes an angle with it equal to the elevation set on the arc. Q. Name and point out the following parts of the rapid-fire sight: Telescope, objective, eyepiece, interior and exterior deflection-scales, micrometer-head, deflection-screw, open sights, dew-cap, lugs, and thumb-screws. A. See Fig. 70. Q. What is one point on the deflection-scale equal to at the target? A. One five-hundredth of the range in yards; thus one Q. Example: The range is 5000 yards, and the drift for that range is found in the range-table to be 12 minutes; how would you set your deflection-scale on the telescopic sight? A. "Fire left" 12 minutes, or 4 points. Q. Why? A. Because drift in our service is always to the right, and to overcome this drift and make the projectile hit the target we will have to fire to the left this 12 minutes due to drift. Q. Example: The range is 5000 yards, and the component of the wind perpendicular to the line of fire is 20 miles, giving from the range-table correction for drift equal to 12 minutes and wind 6 minutes. The wind is blowing from right to left. How would you set your sight? A. "Fire left" 6 minutes. Q. Why? A. Because, as shown above, the drift alone would require the sight to be set at "Fire left" 12 minutes, and if the wind correction is 6 minutes and is blowing from right to left, to overcome this wind and make the projectile hit the target we would have to "Fire right" 6 minutes. Therefore, if the total setting of the sight is to be "Fire left" 12 minutes plus "Fire right" 6 minutes, the final or resultant setting should be "Fire left" 6 minutes. Note.—The corrections for wind and drift are usually found at the same time from a chart, correction-board, or table. Q. Example: The time of flight is 10 seconds (this is found from the gun commander's range-table, knowing the range); how would you determine the correction for travel with a telescopic sight? A. Set the sight at zero. Traverse the gun until the vertical hair cuts the target. Signal: "Stop traversing," and count the number of seconds time of flight (10), moving by the right Q. Example: If you were given the range, a gun commander's range-table, a correction for wind and drift equal to "Fire left" 9 minutes, and the target were moving from right to left, how would you proceed to determine the setting of your sight? A. First, determine by the above method the correction for travel during time of flight (time of flight being found in the gun commander's range-table). Set this on the sight. Suppose it were "Fire left" 3 minutes. Second, use this position of the vertical hair as a new zero, and move the vertical hair to "Fire left" 12 minutes. That is, "Fire left" 3 minutes plus "Fire left" 9 minutes equals "Fire left" 12 minutes. If the travel had been "Fire right" 3 minutes, then by moving the scale "Fire left" 9 minutes, the final setting of the sight would have been "Fire left" 6 minutes. Q. From the table on page 129 find the number of yards 3 points on the telescopic sight are equal to at 7000 yards range. A. 18 yards. TELESCOPIC SIGHT. (Model 1898.) Fig. 69. 3-INCH RAPID-FIRE GUN-SIGHT. Fig. 70. 2. Point or describe the location of the following parts of the telescopic sights, Model 1904:
A. See Figs. 71 and 72. Fig. 71. 3-INCH TELESCOPIC SIGHT, MODEL OF 1904. Fig. 72. 3-INCH TELESCOPIC SIGHT, MODEL OF 1904. Table of Values in Yards of Points of Deflection.
Note.—This table is only approximate. It is true within 1 yard, which is sufficiently accurate for all firing under Case II. Q. Where is the sight placed under cases one, two, and three? A. On the trunnion for case one, to give both elevation and direction. On the sight standard for case two, to give direction only (quadrant elevation is set by the elevating-arc). It is not intended to be used at all in case three, but, of course, it could where the quadrant elevation is to be set by the sight instead of by the elevation-arc. It will then have to be placed on the trunnions. Q. Define cases one, two, and three. A. Case one, where direction and elevation are given by the sight on the trunnion. Case two, where direction is given by the sight, and elevation by the quadrant or elevating-arc. Case three, where direction is given by the azimuth-circle, and elevation by the quadrant or arc. Q. What is the difference between the axis of the bore and the line of departure? A. The jump. (See Fig. 63.) Q. What is the line of sight? A. Line joining the target, the point of the front sight and the peep of the rear sight; or with telescopic sights, the line joining Q. Define time of flight. A. The time it takes the projectile to leave the bore till it strikes. Q. What is a tangent? A. A straight line which touches but one point on the circumference of a circle and is perpendicular to the radius at that point. Q. Define angle of fall. A. It is the angle which the tangent to the trajectory at the point of impact makes with a line parallel to the line of sight at this point. Q. What is the line of departure? A. The prolonged axis of the bore at the moment the projectile leaves the muzzle. Q. What is the line of fire? A. The prolonged axis of the bore before the gun is fired. Q. What is the axis of the bore? A. The line passing through the centre of the bore from breech to muzzle. Q. What is the angle of departure? A. The angle included between the line of departure and the horizontal plane. Q. Define drift. A. It is the deviation due to the rifling in the gun to the right or left of the vertical plane passing through the axis of the bore, or plane of fire. It is always to the right in the U. S. service. Q. To what in a telescopic sight does the front sight on an open sight correspond? A. The intersection of the cross-hairs. Q. To what does the rear sight correspond? A. The eye-lens. Q. What is the trajectory? A. The path of the projectile in the air. Q. How is the velocity of the wind determined? A. By the anemometer. First take the reading of the discs For example: Suppose at 10:05 A.M. the reading is 62 miles, and at 10:11 A.M. the reading is 63 miles. If in six minutes it goes one mile, in sixty minutes it will go ten times, or ten miles per hour. THE ANEMOMETER. Fig. 73. Q. How are the components of the wind in the direction of the line of fire and in a lateral direction determined? (See Fig. 74.) A. First: Set the arrow on the disc to read the azimuth of the wind. (This is done automatically.) Second: Set the little lever-arm at the azimuth of the line of fire. Third: At the point on the lever-arm reading the velocity of Fig. 74. Q. How are the wind components determined by the "new method"? A. 1o target-pointer to velocity of wind on target-arm. WIND COMPONENT. (New Method.) Fig. 75. THE AEROSCOPE. Fig. 76. DIFFERENCE CHART for 10 in. B.L.R. No.1 in Battery __________, Fort __________ Directing Gun of that Battery 10 in. B.L.R. No.2 Azimuth of Gun No.1 from Directing Gun, 79°03' Gun Displacement, 38 Yards. Fig. 77. Fourth: From this same point on the little lever-arm run a pencil along the nearest line parallel to the arrow, and where it intersects the diameter of the disc perpendicular to the arrow is read the component in the direction of deflection or the lateral component. Q. What is a difference chart? A. One that determines the differences in azimuth and range between the directing-gun and the gun for which it is constructed. It consists of a board having drawn on it circles of different diameters, which are the azimuth difference circles (the amounts being written on each circle). (See Fig. 77.) Q. How is it used? A. First: Set the range-arm on the given azimuth. Second: Run the finger to the given range on the range-arm. Third: The azimuth difference is read on the nearest circle that cuts the point where the finger last rests, and the range difference is read on the scale in red ink along the azimuth circle of the board. (See Fig. 77.) Q. What is meant by muzzle velocity? A. The number of feet per second a projectile is moving at the time it leaves the muzzle of the gun. It is also called Initial Velocity. Q. From the following gun commanders' range-scale find the time of flight, sight elevation, and quadrant elevation for 4120 yards range. Gun Commanders' Range-scale. I. V. 2200. 8-inch B. L. R. Smokeless powder.
ELECTRICAL DEVICE FOR OPERATING ANEMOMETER STOP-WATCH. Fig. 78. A. 6-1/5 seconds, about; 1° 1' minus (depression); 4° 18' plus (elevation). The Atmosphere-board.Q. Describe the atmosphere-board. A. This is merely a graphic table by means of which the reference-numbers to be recorded on the atmosphere-aeroscope indicator can be determined from the readings of the barometer and thermometer. The arguments are barometer and thermometer readings, and the reference-numbers are indicated by diagonal lines. The thermometer axis is horizontal and the barometer axis is vertical. To increase the ease and rapidity of reading the barometer scale is graduated on a movable T square. The method of construction is shown in Fig. 79. Operation.—Set the T square for the thermometer reading and note the diagonal line which intersects the fiducial edge of the T square the nearest to the barometer reading. The atmosphere dial is graduated to ½ per cent. The reading of the board should be taken to the nearest half reference-number. ATMOSPHERE BOARD Fig. 79. SPECIAL APPARATUS FOR MORTARS.Q. Point to the following parts of the Mortar Gun-arm:
A. See Fig. 80. SET-FORWARD RULER.Q. Describe the set-forward ruler and explain its use. A. First find the travel in yards per minute. Set the pointer (a) on the slide (b) at the number of yards on the scale of "yards travel per minute (c)." Then on gun-arm get time of flight for that point. The "set-forward point" will be the reading opposite time of flight on the scale of "yards travel during time of flight +1 minute (d)." (See Fig. 81.) Example.—After taking four observations on a target we find that in one minute's time it has traveled 200 yards. Set the pointer (a) at 200 yards on the scale (c). On the gun-arm we see that the time of flight for this point is sixty seconds. Therefore our set-forward point is 400 yards, as this is the reading exactly opposite the time of flight on scale (d). (See Fig. 81.) Q. Describe and explain the use of the prediction scale. A. The prediction scale is graduated in the same manner as the gun-arm (1" = 300 yards), and is used for finding the predicted point. After having marked four points on the board, showing the course of the target, place the prediction scale so that zero (0) is on the last point, or reading, and then mark off as many yards in advance of the last point as the first reads from zero. This point is known as the predicted point, and is used by the range officer only. As soon as the predicted point is found he sets his azimuth instrument at the given azimuth and when the target crosses the vertical wire in the instrument, he gives the signal "Fire." (See Fig. 82.) GUN ARM FOR MORTARS. Fig. 80. Fig. 81. THE SET FORWARD RULER FOR MORTARS. Fig. 82. THE PREDICTION SCALE. DEFLECTION SCALE.Q. Describe the deflection scale and explain its use. A. The deflection scale is used to determine azimuth corrections for mortars. After the "set-forward point" has been obtained, the plotter sets the gun-arm on it and by means of the indicator determines the zone, range, and elevation of the target. The operator reads the straight azimuth from the gun-azimuth scale and gets the zone and elevation from the plotter. He then sets the elevation scale-pointer at the given elevation, turns crank moving small azimuth pointer to the azimuth he obtained from gun-arm scale; then by referring to the large azimuth scale-pointer he reads the corrected gun-azimuth, which he sends to the pits together with zone and elevation. Should it become necessary to make a correction for drift, turn the deflection-scale knob, either to right or left, as the case may be, as 3 = normal. (See Fig. 83.) Note.—This apparatus depends upon the fact that the drift is the same for the same elevation in every zone except the eighth. In this zone the instrument cannot be used as now constructed. WARSHIPS.Q. State the general appearance, average length, beam, draft, speed, tonnage, thickness of belt and deck armor of battleships, armored cruisers, protected cruisers, torpedo-boat destroyers, and torpedo boats. A. See Table "A." Q. Point from Figs. 84 and 85 the following:
Fig. 83. THE MORTAR DEFLECTION SCALE. TABLE A.--TABLE OF WARSHIP CHARACTERISTICS.
Q. What vessels are unarmored? A. Gunboats, torpedo-boats and destroyers. Q. What is the best part of a ship to attack at long range? A. The decks. Q. What part should rapid-fire guns attack at short range? A. Sides, ends, and small turrets, and guns protected only with shields. These rules, however, may vary with height of battery, form of attack, and class of ships attacking. Q. How are ships of the U. S. Navy distinguished, knowing their names? (See Fig. 86.) A. Battle-ships are generally named after States (except the Kearsarge), cruisers after large cities, gunboats after historical cities as a rule, coast-defense monitors have Indian names, torpedo-boats and torpedo-boat destroyers are named after heroes of wars. (The above rules have a few exceptions.) Q. From the silhouettes on Fig. 86, Ships of the U. S. Navy, find a battle-ship, a high-speed cruiser, a gunboat, a coast-defense monitor. Fig. 84. Fig. 85. Fig. 86.
A. Signal numbers 20, 30, 23, 6. Q. Find from Figs. 86 to 93 inclusive, a battle-ship, cruiser, monitor, and gunboat of the navies of Germany, France, England, Japan, and Russia. Fig. 87. Q. What thickness of Krupp cemented armor will a six-inch gun penetrate at 5000 yards? An eight-inch gun? A ten-inch gun? A twelve-inch gun, model 1895? A twelve-inch, model 1900? A. Six-inch penetrates 3 inches; eight-inch, 5 inches; ten-inch, 7 inches; twelve-inch '95, 10 inches; twelve-inch 1900, 12 inches. (See Armor-attack Sheet, Fig. 87.) SILHOUETTES OF SHIPS OF RUSSIAN NAVY. Fig. 88.
SILHOUETTES OF SHIPS OF GERMAN NAVY. Fig. 89.
SILHOUETTES OF SHIPS OF FRENCH NAVY. Fig. 90. Fig. 91.
SILHOUETTES OF SHIPS OF JAPANESE NAVY. Fig. 92.
SILHOUETTES OF SHIPS OF ENGLISH NAVY. Fig. 93. Fig. 94. Fig. 95.
CODE FLAGS AND PENNANTS INTERNATIONAL CODE OF SIGNALS U.S. STORM SIGNALS Flags 8 feet square. Pennants 5 feet hoist, 12 feet fly U.S. WEATHER-BUREAU SIGNALS Fig. 96. [To face page 168.] EXPLOSION OF A SUBMARINE MINE BY THE GUNNERS OF THE 54TH CO. C. A., FORT TOTTEN, N. Y. (Observation Firing on a Miniature Battleship used as a Target.) [To face page 169.] EXAMINATION FOR TORPEDO-COMPANY GUNNERS.SECOND-CLASS GUNNERS.Ammunition, Nomenclature, and Service of Piece. Note.—In the following series of questions and answers the new and adopted system only is included. Q. What guns are usually assigned to torpedo companies? A. R. F. guns, principally 3-inch. Q. Give a rough outline of the general operation of the system of submarine mines. A. A submarine mine is a ball-shaped iron case filled with high explosive. Several of these are planted across a channel and held below the surface of the water by heavy anchors. From each mine is run a single-core cable. All these cables join the wires of a multiple-core cable which runs to the "mining casemate." In this building are electrical devices for firing the mine either when it is struck by the enemy's ship (called "contact-firing,") or at the mine-commander's will ("observation-firing"). This firing is accomplished by sending an electric current through the cable to the mine. Inside the mine is an electric fuse. The return-circuit is by ground. (The details of electrical and engineering features and wiring are not required of a second-class gunner.) Q. What ammunition is used in the 3-inch R. F. gun? A. A cartridge case of solid drawn brass about 23 inches long containing a powder charge in the base of 5 pounds of smokeless and a projectile weighing 15 pounds in the top. Armor-piercing shell and shrapnel are also used. The saluting charge weight, 2 pounds. Q. What primer is used? A. The Frankford Arsenal 110-grain igniting. (See No. 2, Fig. 97.) Q. Name the principal parts of this primer. Fig. 97. IGNITING PRIMERS FOR R.F. GUNS NO. 1 IGNITING PRIMER FOR FIXED AMMUNITION NO. 2 10 GRAIN IGNITING PRIMER NO. 3 20 GRAIN IGNITING PRIMER A. Body, obturating-cup, vent-closing disc, primer charge, end-closing wad. (See No. 2, Fig. 97.) Note.—The following data is given for general information only: Weight of the piece, 1722 pounds. Length, 154·5 inches. Length of bore, 50 calibers. Number of grooves, 24. Twist of rifling, 1 in 50 calibers at the breech and increasing to 1 in 25 at the muzzle. Kind of powder, smokeless. Weight of charge, 5 pounds. Weight of projectile, 15 pounds. Muzzle velocity, 2600 feet per second. Muzzle energy, 702·9 foot-tons. Penetration in steel, at the muzzle 5·37 inches; at 1000 yards, 3·82 inches; at 2000 yards, 2·72 inches; at 3000 yards, 1·94 inches. Q. Point out the following parts of the breech-block:
A. See Figs. 17 and 19. Q. What acts as the gas check? Q. How should a 3-inch R. F. breech-block be cared for—kind of oil, etc. A. Same as for any other heavy gun. (See first part of book.) Q. Describe how the extractor and firing pin work. A. (This will have to be done at the gun.) Q. Describe the action of the lever handle. A. (Do this at the gun.) Q. Point out the following parts of the gun and mount (masking parapet mount):
A. See Figs. 17 and 19. Q. How are rapid-fire guns cared for and kept in working order? A. Same as the 12", 10", 8", 6", etc. (Given under heading for second-class gunners, Gun-companies.) Q. How many men constitute a gun detachment for the 3-inch R. F. gun (masking parapet mount) and give the posts of each? A. Chief of detachment, gun-pointer, and 5 men. POSTS.
The posts of the gun detachment as given above are for inspection and preparatory to the service of the gun. The men resume their posts on the completion of any duty requiring them elsewhere. The chief of detachment and gun-pointer go wherever their presence is necessary. Q. Give the duties of the gun commander, chief of detachment, and gun-pointer. A. The gun commander indicates the target, repeats the commands "Commence firing" and "Cease firing," announces the The chief of detachment is responsible that the gunner identifies the target. He is particularly charged with seeing that his piece is properly loaded and that the precautions for safety in case of misfires are carried out. At the command "Cease firing" he will cause the breech to be opened. The gun-pointer is responsible for the proper regulation of the current for the lights of the night sights. He adjusts the sight in its seat and sets the elevation and the deflection scales for the indicated range and deflection. He aims the gun and fires as soon after the command "Ready" as the piece is aimed. He will observe the splash of his shots if possible and when necessary make the proper correction on his sight. In connection with the gun commander he determines the deflection correction for travel of target, using the deflection scale for the purpose. Q. Give the duties of the members of the detachment for loading and firing. A. The chief of detachment indicates the target and range and commands: 1. No. —, 2. With (such projectile), 3. Commence firing (or, so many rounds, commence firing). He repeats the command cease firing. After the first round the projectile is named only when a different kind is ordered and the gun is loaded without command immediately after it is fired. The gun-pointer, when the gun has the proper elevation, commands and signals clamp. He fires by lanyard and in simulated firing calls out fire when he pulls the lanyard, as a signal to load. No. 1 opens the breech, closes it as soon as the cartridge is inserted, and calls out ready as soon as he is clear of the recoil. (If there is any difficulty in opening or closing the breech, he examines the threads of the breech-block, wipes off any dirt found, and oils the mechanism.) No. 2 receives a round of ammunition from No. 5 and inserts it in the chamber. (If there is difficulty in opening or closing the breech, he examines the threads of the breech recess, wipes off any dirt found, and oils the threads if they become dry.) No. 3 clamps the gun in elevation at the gun-pointer's command and unclamps immediately after the gun is fired. No. 4 receives the empty cartridge case as it is ejected and lays it aside. No. 5 brings a round of ammunition of the designated kind from the recess and passes it to No. 2. MATERIAL AND DUTIES OF THE LOADING-ROOM.(Except electrical principles involved.) Q. What apparatus is used in making a Turk's head? A. A navy knife and tool-box "D" is required. Besides the tools the box should be equipped with a supply of Turk's head collars and marline. Q. What is used in making a telegraph-joint? A. A pair of pliers, navy knife, and, where insulation is desired, okonite tape. Q. What is used in making a joint to be used under water? A. A navy knife, tool-box "D," junction-boxes in which to clamp the Turk's heads, and the material for making okonite joints or the cores. These materials are, okonite tape, cement, Manson tape and tin-foil. A torch is needed for vulcanizing the joint. Brass jointers are sometimes used in making the joints. Q. Point out all the parts of an assembled mine. A. See Fig. 98. AN ASSEMBLED MINE Fig. 98. Q. Point out the following parts of a compound plug: circuit-closers; transformer; loading-wire; fuse-wires; fuses; fuse-can; bursting-charge; set-screw for fuse-can; lead or graphite gasket for same; rubber packing; brass washers; fuse-can cap; lower tube set-screw; gland; lower tube; plug proper; loading-wire. Q. Name some of the duties in the loading-room. A. Loading mines with explosives; assembling them complete to the single-core cable; preparing compound plugs, cables, and raising-ropes; in other words, preparing a mine for planting in the harbor, except attaching the anchor and mooring-rope. Q. Make a telegraph-joint. A. See Figs. 99 and 100. Q. Make a Turk's head. A. See Fig. 101. Trim the ends square: 15 inches from it place a wrapping of a few turns of marline overlapping each other and secured by a square knot. Slip on the collar, flat side against the stop of the marline; bend the iron wires back over the collar and cut off 4 inches from one and 6 inches from the next, alternately. Bend the wires with the pliers as so to closely fit and crimp the collar. Beginning at the Turk's head, wrap closely with marline so as to bind the wires to the cable. The jute covering and serving maybe bent back over the wires, or it may be cut off: in cutting turn the edge of the knife away from the cable. Q. Make a taped joint, place it in salt water for 30 minutes and test. A.
Q. How is a taped joint vulcanized when in the "distribution-box boat"? TELEGRAPH-JOINT MADE WITHOUT BRASS JOINER. Fig. 99. TELEGRAPH JOINT WITH BRASS JOINER. Fig. 100. TURK'S HEAD. Fig. 101. A. By tying a piece of waste soaked in kerosene to a wire lighting, and using this as a torch for heating the joint. Q. Explain the method of preparing a compound plug. Fig. 102. A. This will have to be learned by practice and constant instruction at the loading-room. Note.—The transformer, fuse, can, etc., on the compound plug are still in a state of experimentation and no method for the assembling of the latest design has been adopted as yet. Q. How do you test the transformer? A. With a circuit detector or galvanometer and a dry cell, as shown in figure. Note.—In case of a break in the coil, Fig. 102, there would be no current flowing in galvanometer and no deflection of the needle would be indicated. The wires that should show closed circuit are the two red wires and the black wire and transformer case. Those that should be open are the black, and either red wire. (See Fig. 102.) Q. How are fuses tested? A. With a dry cell and a circuit detector. A closed-circuit test is all that is necessary. This should always be done under the supervision of an experienced electrician. Q. What apparatus is used in preparing a compound plug complete? A. Bench vise, S-wrench, large monkey wrench, screw driver, small pliers, navy knife, loading wire, cotton-braided wire, priming charge, fuses, rubber packings, brass washers, followers, lead washers, set screws, red lead or ruberine, circuit detector, brass jointers, rubber tape. Q. What is the method of numbering mines? A. Facing in the direction of the expected approach of the enemy's ships, mines are numbered from left to right, beginning with No. 1. Q. How are groups numbered? A. In the same manner. No. 1 group on the left, No. 2 next toward the right, etc. Q. How are the mooring-ropes prepared, and what are the rules for length of mine cables and of mooring-ropes? A. The mooring-cables are cut off with square ends and the ends passed through the holes in the mooring-sockets. The strand and wires are untwisted and spread out for a length equal to the length of the socket-hole. The rope is then pulled back until the loose ends are about flush with the top edge of the hole; a piece of marline is tied about the rope below the socket. If necessary Mines are planted with a submergence of 5 feet below mean low water. Where ordinary anchors are used the mooring-ropes must be prepared for depths obtained by sounding. If sockets are used, the ropes for No. 32 cases are but 10 feet less than the ascertained depths at mean low water. This allows 5 feet for submergence and 5 feet for mine, mine bail, sockets, shackles, and anchor. For the larger mine cases an additional allowance must be made for the length of the cylindrical part of the case. Finally each mooring-rope is tagged at each end with the number of the corresponding mine. Mine cables are cut to the following lengths, plus twice the approximate depth of the water: Each end of each cable is tagged with the number of the corresponding mine. MATERIAL FOR AND DUTIES ON THE WATER.Q. What apparatus is taken out on the distribution-box boat? A. One distribution-box, 1 buoy for same, 1 mooring-rope for attaching buoy to distribution-box, 1 anchor sufficiently heavy to hold distribution-box boat, 1 anchor buoy (keg), and rope for same, 2 anchor shackles (1 for anchor and 1 for box), 1 pair field glasses, alcohol, 2 alcohol lamps, cable tags, Turk's head, collars, cotton waste, 2 files, 2 hammers, 2 heavy lines, knives, marline, 2 marline spikes, 1 megaphone, 2 monkey wrenches, 2 pliers, protective tape, rubber cement, rubber tape, 2 scissors, tin-foil, telephone, brass connectors, lashings. The planter may locate the distribution-box boat anchor, and in that case it, together with its buoy, would not be taken out in the distribution-box boat. Q. How and in what way are the cores of cable numbered? A. They are numbered by the non-commissioned officer in charge of the boat, who establishes communication with the casemate, using the boat telephone, and working under the instructions of the casemate electrician. Nos. 1, 13, and 19 are easily selected by means of their special marking; No. 19 is the center core; No. 13 is the marked core in the inner row of six; and No. 1 is the marked core in the outer row of twelve. In the seven-cored cable there are no marked cores, the cores being numbered under the instructions of the casemate electrician. Q. How is multiple cable laid? A. It is transported to the planter by tramway, hoisted by steam-derrick to the forward jacks; it is then joined to the "shore ends" of the cable; the planter then steams to the distribution-box buoy and passes the end of the cable to the distribution launch, where a Turk's head is made and all is ready to receive the single-core cables for planting. PLANTING OF MINES.Q. How are single-core cables prepared? A.
Q. Describe how to place mines aboard and to attach to cables preparatory to being planted. A.
Q. Explain how to sling the mine and anchor, and prepare it to "let go."
Q. Describe the method of planting. A. The planter now moves to the distribution-box boat, the latter to the port, No. 10 cable is passed to the same, planter now moves to No. 10 buoy, and when mine is abreast, the command "let go" is given. The tripping hook of the mine is released first, and that of the anchor immediately after. The planter now circles to starboard, passes to the rear, and comes up to the distribution-box boat to the starboard. No. 9 is now passed, and planter moves forward to the position of this mine, plants it, and returns to distribution-box boat to repeat the operation till the group is planted. CAUTIONS TO BE OBSERVED.Men operating tripping hooks keep their feet free from all cable. Men on after deck must keep entirely free of all cable while being spent when planter is passing from distribution-box boat to mine buoy. If dynamite is used as explosive all mines should be covered with paulines or burlap to protect them from the direct rays of the sun. Q. Name the apparatus on the boat used in planting mines. A. Derricks, catheads, snatch-blocks, steam-winches, insulated cable, cable-drum frames, circuit detector, boat-hooks, Q. Give a method for marking the positions at which mines are to be planted. A. The distribution-box is located first, a buoy and anchor being used as the mark. The center point of the group is located next, then the two ends of the group. The launch is directed over the spot selected from the map for the distribution-point by means of base-end instruments at the primary and secondary stations (these two instruments being set at the azimuth of the selected spot), and by signals from these stations the launch drops the anchor and buoy when it is at the intersection of the vertical cross-wires of each instrument. The launch marks the center of the group by moving approximately perpendicular to the line of mines to the desired distance. The line of mines is then determined by taking bearings and objects on shore (previously determined from the map) or by a similar method to that of locating the distribution-box buoy. Small planting-buoys are used for this purpose. The distribution-box buoy is usually a large keg or vinegar-barrel. Q. How are soundings made? A. By starting from either end of the "located group" and making a sounding at every 100 feet. Small Boat Drill.Q. Explain how a small boat used for marking and locating is managed, and give the commands necessary. A. Upon leaving wharf, "Shove off!" performed by designated man. To raise oars preliminary to rowing: "Up oars!" all oars being held vertically, opposite rowlocks, blades athwart boat. To lower oars into the water: "Let fall!"; all oars are dropped easily into the water, without splashing, and quickly adjusted into the rowlocks, and then held in position of "Oars!" (See below.) To move the boat forward: "Stand by to give way together!—GIVE WAY TOGETHER!" the boat being propelled forward at the latter command, all the men taking a slow uniform stroke, being guided by No. 1, feathering their oars as they come out of the water and move forward. To cease rowing temporarily: "Oars!"; at this command the oars are raised out of the water to a horizontal position, blades parallel with the surface of the water. To rest without taking oars from rowlocks: "In oars," when oars are drawn in and placed with handles under gunwales on opposite side of boat from rowlocks. To move backward a short distance: "Back water!" executed opposite to "Give way together!" To stop boat: "Hold water!"; the oars are held rigidly in the water, blades vertical. To stop boat quickly, as if running on a rock: "About face! hold!" when the oarsmen turn about and hold blade in water, stopping momentum of boat. To turn to port: "Pull starboard, back port!" (To turn to starboard, the opposite). To make a landing: "In bow!"; the bow oar is raised vertically, then lowered into its place in the boat, and the bow man takes the boat-hook and guides boat gently into its place. To cease rowing: "Way enough!"; the oars are raised vertically, shoved properly in place. CORDAGE.Q. Name the important knots used in mine-work. A. Anchor-knot or fisherman's bend, square knot, clove-hitch, bowline, stopper, whipping, and short splice. (See plate of knots for gun-companies.) THE U. S. MAGAZINE RIFLE.See Examination for Second-class Gunners, for Gun-companies. FIRST-CLASS GUNNERS.CARE AND PRESERVATION OF MINE MATERIAL.Q. How are mine-cases preserved and cared for? A. They are painted light gray on the outside, and the screw-threads covered with a mixture of lard-oil and white lead (4 parts of tallow to 1 white lead). They are also either painted or covered with protective material on the inside. They are then stored on suitable racks inside a "torpedo storehouse." Q. How are all bearing surfaces, such as screw-threads, prepared for storage? A. By first thoroughly cleaning them with brushes, kerosene, waste, etc., and then covering with the above mixture of white lead and tallow. Q. How is the motor-generator cared for? A. Fill all oil-holes, and keep all parts free from dust and foreign material; see that all connections are tight; see that all brushes are in good condition, and replace worn ones by new ones. Use very fine sandpaper for slight inequalities of the commutator. Q. How are the mine-panel and the switchboard cared for? A. See that all bolts to busses are tight, that all lamps are screwed home, that all contacts are clean and free from gum or dirt, that all switches work properly and all contacts correctly made. Q. How should electric lights be cared for? A. They should be kept clean and polished. Any snap-switch that sparks badly should be replaced. No verdigris should be allowed to accumulate on any brass fittings. When a lamp becomes dull or black inside, a new one should replace it. When any fuse is blown out, new ones should be put in. (Never use copper wire as a substitute for a fuse.) Q. How should transformers be cared for? A. Simply kept clean and in a dry place. They should be tested with a circuit-detector once in a while. Q. How is the charging-generator cared for? A. Keep free from dirt or rust, fill all oil-holes, clean the commutator with a dry rag, keep the brushes set so as to make good contact, and when not in use cover with a rubber paulin. Q. How is the oil-engine cared for? A. The oil-engine should be kept clean and nicely painted, all oil-holes filled, the water-tank filled and free from mud and sediment, the vaporizer examined from time to time and kept free from packed carbon, the piston clean and well oiled, the poppet-valves tight and free from any clogging material, the starting-torch clean and free from soot. Q. When putting a piece of machinery out of commission what is done? A. All bearing surfaces are exposed, cleaned, and covered with white lead and lard-oil or a similar substitute preservative. All small loose parts are removed, covered with cosmic wrapped in burlap, and stored under cover. The machine should also be housed. Q. Name some of the principal cleaning materials. A. Steel scrapers, button and wire brushes, waste, pomade, Q. Name some preserving materials. A. Cosmic, white lead, red lead, raw linseed oil, turpentine, beef tallow, drier, lamp black, pumice stone, varnish, asphaltum varnish, paint brushes, shellac, graphite paint and insulac. Q. Name some uses of each. A. Cosmic: Covering bright parts of engines, generators, motors, etc., when out of commission. White Lead: (4 pts. W. L. to 1 of tallow) Used on screw-threads of mine cases, steel threads, compound plugs, bolts, nuts, washers, surfaces of flute joints, etc. Caution: Never use this on a joint where electrical contact is to be made. Red Lead: (100 pounds red lead ground in linseed-oil with 5 gallons raw linseed added.) On mine cases after being scraped. As a preliminary coat for iron surfaces of engines, generators, etc. Raw Linseed, Turpentine, Drier, and Lampblack, for making different kinds of paint. Turpentine is also used to clean brushes, etc. Tallow: For mixing with white lead to form a preservative. Pumice-stone: When powdered and mixed with oil is used to rub down surfaces, as the first coat of varnish on an engine. Varnish: As a finishing coat for metal and wood surfaces not exposed to heat or water. Asphaltum Varnish: For painting anchors, distribution-boxes, mooring-sockets, shackles, sister hooks, junction boxes, iron work of operating boards and power panels, etc. Shellac: For covering decks, spars, etc. Graphite Paint: For painting hot parts of engines, etc. Insulac: For preserving insulation on electrical instruments, etc. Q. How is an engine painted? A. All hot surfaces should be painted with black graphite HANDLING HIGH EXPLOSIVES.Q. Name some high explosives used in submarine mining. A. Wet gun-cotton principally, dynamite, and other high explosives that can be readily purchased in commercial life in case of emergency. Q. Why is wet gun-cotton to be preferred as a high explosive? A. Because it is perfectly safe to handle. It can only be detonated by first detonating a small piece of dry gun-cotton placed near it. Q. What are some important precautions to be observed when loading mines? A.
Q. How is dynamite that is frozen thawed out? A. Place the frozen dynamite in an open watertight can. Place this can in another can of warm water, such that the heat of the warm water only will do the thawing. KNOWLEDGE AND USE OF THE PLOTTING-BOARD AND AZIMUTH INSTRUMENT.Q. Describe the plotting board. A. It is the same as that used for guns except the gun arm and its parts are not used. The scale is ordinarily 100 yards = 1 inch. Q. How is it used for mine firing? A. The ship is tracked by plotting points of intersection of the primary and secondary arm every 20 seconds. After several positions are plotted a point is predicted at a certain interval of time ahead and by means of a "combination prediction and speed scale" the time of the arrival of the ship over the mine which was previously plotted on the board is obtained and this is the time of firing that mine. This is called "judgment firing." Q. Describe and use the azimuth instrument. A. See Examination for First-class Gunners for Gun-companies. BATTERIES, GENERATORS, AND SEARCH-LIGHTS.Q. Name the batteries used in mine work. A. Casemate battery (storage—40 cells) and boat telephone battery (either storage or dry cells sufficient to give 15 volts). Q. Describe the casemate battery. (See Fig. 103.) A. This is a storage-battery of the standard chloride accumulator type. It is composed of 40 cells, type D-5 (D = size of plate 5, the number of plates). D-5 has two positive and three negative plates, each 6" × 6". Positive plates are of a brownish color, negative grayish. These plates are contained in a glass jar nearly filled with electrolyte (one part sulphuric acid to five parts distilled water by volume makes electrolyte of 1·210 specific gravity. The acid must be poured into the water.) These glass jars are placed in trays of sand and the trays rest on glass insulators. The normal charge and discharge rate of this battery is 5 amperes, although in starting the motor generator a much higher current is drawn from the battery. The voltage is about 80. Q. What precautions are necessary to keep it in order? A.
STORAGE CELL (DISMANTLED) Fig. 103.
Q. Describe a searchlight. A. It consists of an iron cylinder mounted on an iron pedestal in a yoke. The cylinder contains a parabolic mirror in the back, a series of glass strips in the front, and two "carbons" in the middle. The electric current in passing through the carbons heats the points to a very high degree, producing a brilliant light. This light is reflected by the mirror towards the front, and the mirror, being of a curved form, also converges the rays of light. Underneath most searchlights are electric motors for traversing and elevating, and these motors are started or stopped by means of switches in a contrivance called a "controller," which is always placed at a distance from the light. Q. Point out the following parts of a 36" searchlight: hand star-wheel for slow vertical movement; wheel for throwing out split nut used for connecting or disconnecting the drum from the base mechanism; wheel for slow horizontal movement; hand star-wheel for clamping turntable to center-pin for electrical control; wood handles on drum for moving drum by hand; hand-wheel for clamping hand star-wheel A when electric control is used; controller-switch; controller-handle; controller fuse-box; controller-coupling for connecting cable from the projector; focusing-screw; socket for inserting wrench to operate lamp-switch used for cutting out feeding-magnet; socket for inserting wrench when feeding by hand; door used for adjusting the carbons and for cleaning the front door; door used when carbons are to be adjusted or changed; front door; door used when adjusting negative carbons or cleaning the mirror; horizontal peepsights; vertical peepsights; sliding case to be opened when lamp mechanism is to be inspected; projector main switch; latches for fastening base-sheeting; base-sheeting. A. See Fig. 104. 36-INCH SEARCHLIGHT AND CONTROLLER. Fig. 104. Q. Describe the principal parts of the charging-generator? A. The frame holds the field-magnets within which revolves an armature consisting of a winding of conductors and a commutator. Brushes made of carbon touch the commutator. The base rests on guides which permits of a motion of the generator to take up the slack of the belt. Q. Point out the following parts of the generator: frame, base, field-coil, commutator, brushes, shaft, pulley, adjusting-screw, rocker-handle, magnet-frame bolt, brush-holder, brush stud-cable, rocker, bearing-cup, journal-box, pole-shoe, pole. A. See Fig. 105. Q. Point out the following parts of the oil-engine: cylinder-casing, vaporizer, vaporizer-cap, vaporizer-cover, vaporizer-cover lid, valve-box journal, valve-box sleeve, spray-nozzle, horizontal valve, horizontal-valve spring, vertical valve, vertical-valve spring, valve-box, valve-box screw-cap, valve-box coupling, overflow-glass, oil-pump can, oil-pump plug, oil-pump plunger, oil-pump plunger-spring, oil-pump plunger-head, oil-pump plunger-head guide, oil-pump gauge, oil-pump body, bed-plate, bearing-cup, splasher, oil-tank, oil-filter, filter-cock, worm-gear, gear-wheel, gear-guard, crank-shaft, crank-pin oiler, piston, connecting-rod, cam-shaft, governor-wheel, governor-pinion, governor-counterpoise, crank-shaft, governor-balls, governor-counterweight, air-valve cam, exhaust-valve cam, cam rollers, cam shifter, locking-handle, air-valve, exhaust-valve, cylinder-lubricator, cylinder-lubricator pulley, fly-wheel, fly-wheel key-guard, splasher. A DIRECT-CURRENT GENERATOR. Fig. 105. HORNSBY AKROYD OIL-ENGINE. Fig. 106. A. See Fig. 106. Q. Name some important points to be observed in caring for the generator. A.
CASEMATE APPARATUS.Q. Point out the following parts of the power panel:
A. This must be learned at casemate. Q. Point out the following parts of the operating panel:
The terminal block is provided with binding posts and clips. A. This must be learned at the casemate. Q. What is a motor generator? A. A combination of a separate motor and a generator connected to the same shaft. Q. What kind of a motor generator is the one in the casemate? A. It consists of a motor driven by direct current and a generator which delivers alternating current. It has about 1-1/3 H. P. Q. What is the voltage of each? A. 80-110 for the motor and about the same for the generator. Q. What is the object of the casemate transformer? A. To raise the voltage from about 80 to 500 alternating current. Q. Describe the mine transformer. A. This will be learned in the casemate. Q. Explain what switches you would set on power panel for automatic firing, the board having been previously tested and found by the electrician to be in order. A.
Q. Explain how to set operating panel for automatic firing. A. All contacts, connections, switches, etc., having been previously tested and examined by the electrician and found in order:
Note.—If one or more automatic switches cannot be made to stay up, open the power switch for that mine before closing firing switch. Q. How would you fire by judgment? A. Conditions being as above, lift the automatic switch release of the mine to be fired at the command "Fire". Q. How are mines tested?
Q. Point out and describe the parts of a boat-telephone. A. See Fig. 107. Q. Describe how to connect up and use the boat-telephone.
Q. Point out and describe the parts of a wall-telephone composite artillery type. A. See Fig. 108. Q. Give the tests for telephones. A. 1st. Bell is not rung by its own magneto. Analysis:
THE BOAT-TELEPHONE. Fig. 107. Operator's test:
COMPOSITE ARTILLERY TELEPHONE. Fig. 108.
2d. Bell is not rung by distant magneto. Analysis:
Operator's test:
Can hear but cannot be heard. Analysis:
Operator's test:
3d. Can neither hear nor be heard. Analysis:
Operators' test:
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