DIVING—THE FIRST DIVING-BELL—FIXED APPARATUS SUPPLIED WITH COMPRESSED AIR THE SUBMARINE HYDROSTAT—OPERATIONS AT HELL GATE—DIVING APPARATUS—SUBMARINE EXPLOSIONS—IMPROVED DIVING DRESSES—THEIR USE—WORK OF VARIOUS KINDS DONE WITH THEM—INSTANCES OF THIS—SEEKING THE TREASURE OF THE HUSSAR—SUNKEN SHIPS IN SEBASTOPOL—OPERATIONS IN MOBILE—THE DRY DOCK AT PENSACOLA BAY—THE BEAUTIES OF THE SUBMARINE WORLD—HABITS OF THE FISH—POSSIBLE DEPTH OF DESCENT.

Not only have men in modern times sought to extend their knowledge of the sea by dredging and sounding, but with the appliances of modern science they have attempted to plunge themselves into its depths, and provide the conditions there for not only remaining alive but for working. We have seen that the divers for coral and for pearls are enabled to remain under the surface only at the very outside two minutes, and that even this is such a strain upon the organs of the body that their lives are materially shortened by engaging in such work. Air is so indispensable to human life, that before any one can hope to remain any time under the water, some arrangement must be provided for supplying him with air.

The ancients, of course, knew that man was a breathing animal, they saw that each of themselves carried on this process constantly, but what they breathed they did not know, and they were equally ignorant of why they breathed. The discovery of what the air is belongs purely to modern times. About a century ago the astronomer Halley first proposed the use of the diving-bell, and went down in one he had built, to the depth of about fifty feet. The diving-bell was named from its original form, which was that of a bell, and this name is still retained, though the form of the vessel is changed. The supply of air is kept up by an air-pump worked above water. This is, however, a clumsy appliance in which the diver is limited only to that portion of the bottom on which the bell rests. Where there is either a strong current, or the bottom is very shelving, the diving-bell is embarrassing if not dangerous. In one case it is said that the diver was taken from the bell by a shark. Expert swimmers can dive from the outside, and, passing under the lip of the bell, rise suddenly inside of it, a feat which always surprises those who are in the bell. There is also sometimes danger that the bell may settle in the soft mud, and be held there by suction. Such a case once occurred in New York harbor, when a party had gone in the bell as a sort of pleasure excursion. The difficulty looked threatening, but one of the party proposed rocking the bell, and doing so the water was forced under, and the bell was lifted from the ooze.

As the workmen cannot leave the bell, this difficulty if possible is obviated by moving the bell. Frequently, however, submarine operations are to be carried on only in one spot, as in building bridges, when the foundations of the piers are to be laid, or in building breakwaters; laying the foundations of light-houses, or other similar work. In such cases, structures which in principle are the same as the diving-bell, are frequently employed. The one which was used to build the piers of the magnificent bridge over the Rhine, near Strasbourg is represented in the cut. Each of the piers of this bridge rests on a foundation composed of four large iron caissons, of great weight. Each caisson was open at its lower end. The upper part supported three shafts—a middle and two lateral ones. All three shafts arose above the water of the river. The middle shaft communicated with the open air, and the water rose in it to the level of the river. In this a dredging machine, driven by a steam-engine above, worked at the bottom of the river. The other two shafts were closed at the top. The workmen entering above the stream, closed their means of ingress air tight, and then air was forced in until the water was forced down, and out below, leaving the shafts free. The workmen then descended and filled the buckets of the dredging machine. When they wanted to ascend, they mounted to the upper part of the shafts; the air was let off, the water mounted in the shafts and they stepped into the open air.

The abutments of the bridge over the East River, which is to connect New York and Brooklyn by a suspension bridge, with a span high enough to not interfere with the navigation of the river, were built with a somewhat similar device. The towers upon each side of the river had to be so high that a very deep foundation, going down to the original rock, had to be laid, and the workmen engaged in building it worked in a submarine apartment, supplied with air forced down by a steam engine.

The submarine hydrostat, as it is called, is one of the most ingenious and recent applications of the diving-bell principle. Thirty men may work in it at once, for a number of hours, without any inconvenience; while beside this it enables them at will, to float or sink.

Externally, as will be seen from the upper structure in the cut, the machine is a rectangular box, surmounted with another smaller one, entirely closed except at the bottom. The interior of the hydrostat consists of three principal compartments; the lower figure in the cut represents these in section. The lower one, or hold, is open below, and communicates by a shaft with the upper compartment. Between the upper and lower compartments is a third, communicating with the others only by stop-cocks. The upper compartment is called the between decks, and the middle one the orlop deck. All round the hold and the orlop deck runs an air-tight gallery connected with the other compartments only by stop-cocks. The lower part of this gallery contains the ballast, while its upper part is filled with air or water, according as it is desired to float or sink.

When the hydrostat floats, the hold and a portion of the shaft are filled with water; while the orlop deck, its gallery and the between decks are full of air. The workmen are in the between decks, where are lifting and forcing pumps. When it is desired to sink the hydrostat, the door of the shaft and the hatch of the between decks are closed water and air-tight. The pump is then worked so as to draw water from the outside and fill the orlop deck and its gallery. At the same time the force-pump is used to force air into the hold through a pipe connecting the hold and the orlop deck, and furnished with a stop-cock. As the orlop deck, with its gallery, fills with water the machine gets heavier and sinks, while the hold becomes at the same time filled with air. Though the air thus forced into the hold would tend to float the hydrostat, this tendency is counterbalanced by the filling of the orlop deck with water. When the hold is filled with air, the workmen in the between decks open the shaft and descend to the bottom. A sufficient number remain in the between decks to haul up and dispose of the material excavated, and to attend to the pumps which maintain the supply of air for those in the hold. When they want to rise again, the men ascend from the hold by the shaft to the between decks, closing the shaft again. The air is then let from the hold to the orlop deck and gallery; the hold fills with water, while the orlop deck and gallery become filled with air, and the hydrostat rises to the surface; the men open the hatch of the between decks and obtain free communication with the outer world again.

The dimensions of the hydrostat are as follows: The hold is square, the sides measuring each 26 feet, and being 6 feet 6 inches high. The orlop deck is of the same size. The between decks have the same depth, but are only 16 feet in the sides. The base of the hold therefore covers 676 square feet. This ingenious machine has been already used with the most perfect success in performing various work, such as cleaning out and deepening harbors; searching for lost treasure; removing obstructions in channels, and so on.

One of the most important and interesting pieces of submarine engineering ever done in this country was that undertaken for removing the rocky obstructions in Hell Gate, at the entrance, through Long Island Sound, of New York harbor. The first attempt to remove these was by drilling and blasting, as in an ordinary quarry. This work was, however, quite slow, since the current is there so rapid that operations could be carried on only a few minutes each day at the turns of the tides. The next plan was proposed by a French engineer, M. Maillefert, who had used it with great success in the harbor of Nassau. This plan was entirely new, and had the great merit of being surprisingly cheap compared with those then in use. It dispensed with the costly and difficult process of drilling, but exploded the charges on the surface of the rocks to be removed, while they were covered with the greatest depth of water. Gunpowder burnt in the open air explodes without anything but a harmless flash. The pressure of the atmosphere is not enough to restrain the dispersion of the gases suddenly generated. Under water, though, it is different; its pressure confines the gases and makes them act with destructive effect on all sides. For a couple of years operations were carried on by M. Maillefert with considerable success. But he was hampered by want of means, the money that was spent being raised by private subscriptions; and though the channel was greatly improved, operations were suspended. It was found, too, that this method was of great service in breaking off isolated pinnacles of jagged rock, but when the bed was reached, and the rock reduced to a large, smooth, flat surface, progress in the work became slow, doubtful and costly. This process, however, of exploding charges of gunpowder, under water, by means of an electric battery is very valuable in certain situations.

In 1868 Congress appropriated $85,000 for the needs of Hell Gate, and bids for the work were opened to the public. The contract was awarded to Mr. S. F. Shelbourne, of New York, who proposed to do the work by drilling and blasting, the machinery to be placed on the bottom and worked by a steam pump placed on a vessel above. The rock was to be drilled by mushroom drill, as it was called, a diamond drill worked by a small turbine wheel, driven by steam. This drill was tried on the Frying Pan, one of the worst rocks obstructing the channel, but was found to be too delicate and uncertain of continuous action under the trying requirements of the rough work at Hell Gate. A striking drill was then tried, and a machine was built and put in position, but the very day it was to commence to work it was run against by one of the craft so constantly crowding through Hell Gate, and destroyed. Mr. Shelbourne then retired from any further attempt, and the Government has undertaken it, and placed the management of the operations in the hands of General Newton.

The plan now undertaken is to undermine the whole bed of the river at this point, with a series of galleries connected by transverse galleries, leaving only so much rock standing in columns as shall insure stability to the roof above. When this work is completed, these submarine channels are to be charged with the requisite number of thousands of pounds of nitro-glycerine, and blown up with one grand explosion. This enormous work is now well under way, and is being rapidly pushed to completion. Work is carried on day and night, three sets of workmen being engaged in it, each working eight hours. The drilling has thus far been done chiefly by hand, and is very laborious. The workmen are chiefly Cornish miners, who alone can stand the severity of such mining. They are hardly ever dry while at work, and in the winter their clothes are frequently stiffened by ice. Preparations are however making to use machine drills operated by compressed air.

The operations of this mining under the channel of the East River have to be conducted with great care. Every inch of the way has to be critically explored. Seams of decomposed mica have been met, through which the water of the river ran as through a sieve. In one of the shafts such a seam was met, through which the water poured at the rate of six hundred gallons a minute, and could be stopped only by building a strong shield. The floor of the shaft follows a level about thirty feet below the low-water line. The roof follows of course the general contour of the reef, and to determine this, soundings of a special kind have to be taken. The bed of the stream is covered, except on the highest points of the reef, with a deposit of boulders, marl and organic matter from the sewers of New York, sometimes to the depth of ten or twelve feet. As the exact profile of the solid rock must be known before the miners can proceed, every sounding for determining this—and more than 15,000 have been already made—must be carefully done. The sounding apparatus consists of a float, or raft, supporting a machine like a guillotine or pile driver, by which a three-inch iron tube is driven through the overlying matter to the rock bed. The contents of the tube are then pumped out and an iron rod is used to determine the nature of the rock below. If it is a boulder, a dull thud is heard, and the rod does not rebound. Solid rock returns a sharp clink, and the rod springs back. The bearings of the tube are then taken by instruments from the shore, and the position of the rock calculated by a simple process.

Under the direction of General Newton, other submarine operations are also carried on in New York Harbor for the removal of the rocky and dangerous obstructions known as Diamond Reef, and Coentie's Reef, which lie in the busiest part of the harbor, directly in the track of the numerous ferry boats plying between New York and Brooklyn, and are not only troublesome, but dangerous, especially at low water. To perform this work, General Newton has had a special boat built, a scow, a low-lying, box-like craft, with a confusion of timbers, ropes, chains, and machinery surrounding a huge dome in the center. This vessel is very solidly built, and anchored so firmly that the waves strike against its sides as against a wharf. This strength is important for the work, and also to protect the machinery against the chance collision of the constantly passing vessels in the harbor. The general purpose of the scow is easily comprehended. Its object is to guard the drilling machinery while it is at work; to transport it when necessary, and to support the engines for working the drills. In the center of the scow is an octagonal well, thirty-two feet in diameter, in which is supported an iron-wrought dome for protecting the divers. At the top of the dome is a "telescope," twelve feet in diameter, with a rise and fall of six feet to adapt it to the various stages of the tides. When the dome is in working order, it stands clear of the scow, resting on self-adjusting legs, which adapt themselves to the inequalities of the reef. When the drills are working, the dome is down, out of sight, and the machinery, which at the first glance seems in disorder on the scow, is arranged in order, and is level with the deck. The engines which drive the drills are supported on moveable bridges, thrown back when the dome is up; and the drills work in stout iron tubes passing through the dome, one in the center, and the others arranged round it in a circle about twenty feet in diameter. The dome, when down, serves to protect the divers, so that at any time they can go down to regulate the working of the drills, or perform any other service. Without this protection, the divers could not keep their feet, so strong is the current on a rising or falling tide. The divers are protected by a diving suit; the air is furnished them by a pipe to the back of the helmet they wear, and is forced down by an air pump. When a set of holes are drilled, they are charged with nitro-glycerine, and simultaneously exploded by electricity.

This simple statement serves to show how much the modern methods of conducting such submarine operations are dependent upon the advance in chemistry of modern times. In fact, hardly a single appliance used in such operations, from the steam-engine which drives the drills, to the gutta-percha tubes, and the india rubber suits which enable the divers to descend below the water, but what are inventions or discoveries which belong entirely to modern times, and enable men to-day to perform operations which to the ancients would have really been impossible.

The nitro-glycerine is contained in tin cartridge cases, like mammoth candle moulds, ten feet long and from four to five inches in diameter. They are connected with the battery by wires. The divers go down and place these in the holes which have been drilled, first pulling out the wooden plugs which have been placed in them after they were drilled, to keep them from getting filled with dirt. As soon as the charges are placed, the diver returns to the boat, and it drops far enough from the spot, to be safe from the effects of the explosion, and then, with a few turns of the battery, the nitro-glycerine explodes. Two muffled explosions are heard, the one transmitted through the water and the other through the air, and on the instant a volume of water is hurled perhaps fifty feet into the air, while through the mass jets of water are hurled in all directions two or three times further, together with fragments of rock. The water subsides quickly, and round the spot dead fish come floating to the top, killed by the shock of the explosion. At each blast the rock is broken up over an area of four or five hundred square feet, and the fragments are removed by a grappling machine.

In these submarine operations the divers use the armor which the discovery of india rubber and the process of vulcanizing it has made possible, enabling the diver to descend, and leaving him liberty of movement enough to work. In this, as in almost every other new method, there have been gradual steps of improvement and development. During the latter part of the last century the plan was proposed for the diver to carry down with him a supply of air, compressed into a reservoir which he wore on his back, inhaling the air through a tube. Modified arrangements of this method were in use until, in 1830, the discovery of india-rubber afforded the opportunity which was immediately made use of, to improve the diving apparatus. Various improvements, some of them protected by patent rights, have been made in the construction of this submarine armor, but as perfect a method of making it as any is that designed by two Frenchmen, M. Rouquarol, a mining engineer, and M. Denayrouze, a lieutenant in the French navy. One of the chief merits of this arrangement is that by which the supply of air is furnished the diver. This apparatus the diver carries on his back, and it consists of a reservoir made of steel or iron, capable of resisting great pressure, with a chamber on its top constructed to regulate the influx of the air. A tube from this chamber, terminating in a mouthpiece, is held between the diver's teeth. This pipe is furnished with a valve permitting the expulsion of air, but opposing the entrance of water. The steel reservoir is separated from the chamber by a conical valve opening from the air chamber in such a way as to open only by the force of exterior pressure, that of the air in the reservoir tending to close it. The air from the air-pump is forced into the reservoir, and from this the diver supplies his needs as follows: The air-chamber is closed by a movable lid, to which is attached the tail of the conical valve. The diameter of the lid is a little less than the interior diameter of the chamber, and it is covered with india-rubber so as to be air-tight. It yields to both interior and exterior pressure, rising and falling as the case may be. When exterior pressure is exerted on it, the valve is affected, communication is opened between the air-chamber and the reservoir and a portion of the compressed air from the latter flows into the chamber. Should there be too much air in the chamber its pressure against the movable lid keeps the valve closed.

When in use under water its operation is thus: The diver by drawing his breath takes air from the chamber; exterior pressure is exerted on the movable lid, it falls, causes the valve to open, and air comes from the reservoir to establish the equilibrium, when the lid rises and shuts off the communication between the air-chamber and the reservoir until another inspiration on the part of the diver repeats the action just described. When the workman expires, the valve in the respiratory tube allows the expelled air to escape into the water. This apparatus works automatically; though the air-pump may be worked irregularly, its action is regular. The diver receives just the quantity of air enough for a respiration, and this reaches him at a pressure equal to that to which the rest of his body is subjected, and he is therefore able to breathe without effort or attention. The compression of air heats it, and the breathing of air thus heated is bad for the diver. This has been remedied by the same gentleman, by the modification of the pumps by which the air is forced in the reservoir. The air is cooled by being forced to pass through two layers of water before it reaches the reservoir; and expanding in its passage into the air-chamber it becomes again cooled.

With the use of this apparatus another advantage is gained. When the diver is down the air he expires rises in bubbles to the surface, and by the regularity with which they rise his condition can be easily known. If they cease, it is known that something must have happened, and that he should be instantly hauled up. In the old diving dress the expired air passed into the space between his body and the clothing and out at a valve in the helmet, but as the excess of air supplied to him escaped in this way also, it could not be told from this whether the diver was alive or dead.

So common has the practice of diving become, that in all countries it is a regular profession. A few instances of the advantages gained by it will prove interesting.

In February, 1867, a collision took place in the port of Marseilles between two steamers, the Ganges and the Imperatrice. The last of these lost one of her wheels, and a box of gold in the officers' quarters fell out and sank in the mud. The exact spot where it fell was not known. The box was black and not very strong. The next day an attempt was made to recover it. A lead was sunk at the supposed spot where the box was lost: and two lines attached to it were knotted at distances of a yard along their length. The two divers having descended, took each of them one of these lines in his hand, and, using the lead as a centre, walked round in gradually increasing circles, searching carefully every foot of their way. After working three hours in this way they found the box, and restored it to the delighted owner.

Another most interesting case is that of the Hussar, an English navy vessel, which was wrecked in Hell Gate, in New York Harbor. On the 23d of November, 1780, during the war of the Revolution, and while New York was in the possession of the English, a British fleet entered the harbor. Among them, as convoys, were the Mercury and the Hussar. The first had on board £384,000, mostly in guineas, and the second £580,000, together amounting to about $4,800,000. This large sum was intended to pay the English troops then in this country. The next day the whole of this money was placed on board the Hussar, and she got ready to proceed to New London, Connecticut, which was then a place for the British rendezvous. Before starting she also took on board seventy prisoners, from the prison hulks in the bay, who were confined with irons on the gun deck below. What it was intended to do with these unhappy prisoners is not known, nor does it appear from the records. However, thus freighted the Hussar hauled from the dock, and under the charge of a negro pilot, who, a few days before, had safely carried a frigate through Hell Gate, started on her way through that dangerous passage. When she was almost through, when open water lay only a few rods before her, she struck, drifted off, commenced to fill rapidly, and while the question of backing her was being discussed, she struck again, and soon settled, and sliding from the rocks, sank in ninety feet of water. The officers and crew escaped, but the seventy prisoners, chained below to the gun deck, sank with the vessel, without an attempt having been made to save them.

The vessel herself was a large one, carrying thirty-two guns, and measuring two hundred and six feet in length by fifty-eight in width. In 1794 an expedition from England came over to New York, and for two seasons attempted in vain to raise the wreck by grappling, when they were forbidden to work any longer by the Government of the United States. In 1819 another attempt was made by an English company, who prosecuted their work with a diving bell. The strength of the current here made their efforts of no avail, and they abandoned the attempt. Since then the possible chance of the four million dollars has tempted various other companies to try, and in turn they each abandoned the attempt in despair of success. Within the past four years, however, a new company has been at work, using the newly-invented submarine armor, and during this time a sloop has been lying, dismantled but firmly anchored, about a hundred yards from the New York side of the East River, three-quarters of a mile above Ward's Island. This is the spot where the Hussar sank, with her prow pointing north.

The diver's suit consists of, first, a pair of thick rubber leggings and boots combined. These end at the waist in an iron band furnished with iron clamps. Straps of lead weighing together ninety pounds, and which are made to fit about his ankles and waist, are intended to give him weight enough to withstand the current. On the upper part of his body he wears a large copper helmet, with a strong ring-bolt on the top, and below which, securely fastened to it, is a rubber jacket, ending in an iron band, so constructed as to meet that of the leggings and be tightly fastened to it. The sleeves of this jacket are gathered round his wrists and tightly tied. The jacket is of a more pliable stuff than the leggings, so as to enable him to more easily use his hands and arms. The diver puts on his leggings, and then a hook, attached to the end of a rope passed over a pulley, and worked by the engine, is hooked into the ring on the top of the helmet, and this, with the jacket, is hoisted and let down over his head. Having worked himself into the sleeves, he is as helpless, with the weight of his armor, as an old knight encased in iron was. The front of his helmet has a glass door, covered with wire, in it, which is opened for him, while his companions complete his toilet by tying his jacket sleeves round his wrists; adjusting the iron bands of his leggings and jacket, and screwing them firmly together; and then fitting on his leaden anklets and girdle, screwing on the pipe through which his supply of air is provided, and then shutting the door of his helmet, and securely fastening it, he is ready to be cast off. In his hand the diver carries down a slender cord, with which he signals his wants when below. He is slowly lowered down to the bottom, ninety feet below, where his work is pressing, since he has only the hour before and the hour after the turn of the tide.

While he is down those above are as intent upon his welfare as he is himself. He who has the signal cord, holds the most responsible position. There is a prearranged code of signals, for "more air," "pull me up," "more tools," "pull up the bucket," and so on. His work below has been the destruction of the heavy frame work of the vessel, and right well has it been done; there is but little left of her but the worm-eaten and water-logged knees and beams which formed her bottom, and the chief task of the diver now is, with pick and shovel, to break up the hard conglomerate of sand and gravel which has been compacted by the action of the water and the rusting iron. The only sense the diver has to guide him in these depths is that of feeling, for at this depth it is as dark as midnight. The material he thus collects is brought to the surface in a bucket and carefully looked over.

This work is done at the cost of the Frigate Hussar Company, an incorporated company, with a capital stock divided into forty-eight thousand shares of one hundred dollars each, corresponding to the amount of treasure said to be in the run of the Hussar, and since 1866 it has been steadily carried on. The mass of gold has not yet been found, but from time to time in the loads of mud and sand a gold-piece is found. A lump of silver made of various coins, agglomerated by the action of the water, has been brought up, having some gold coins set in it. Cannon, cannon balls, chains, manacles, piles of gun-flints, silver plate, pewter dishes, the ship's bell, and quantities of glass and earthen ware, with numbers of human bones, have been rescued from the deep. Various museums in the country have specimens of relics brought up from this historic ship. One day a brass box was brought up, and when opened found to be full of jewels, necklaces, ear-rings, and pearls of great value. Being left for a moment on the deck of the salvage schooner, it disappeared, and the second search for it has proved more fruitless than the first.

During the Crimean war, a line of ships and frigates was sunk by the Russians in the harbor of Sebastopol, in the passage between forts Catharine and Alexander. When forced to leave the town, others remaining in the harbor were sunk, so that at least 100 vessels, representing an estimated value of between fifty and sixty millions of dollars, were sunk. To prevent if possible the action of the sea upon their machinery and metallic portions, these were covered with tar or tallow. When the war was over, an American engineer, named Gowan, went to Russia and undertook the job of raising these vessels, after having gone down himself in a diving suit, and satisfied himself of their condition, and that he could recover some of them entire and others in parts. In this work use was made of an enormous pump, raising nearly 1,000 tons of water a minute. With this, after closing as well as could be, the port holes and other openings, another pipe for the introduction of air was arranged, and the pump set in action. This powerful machine emptied the vessel of water in a very short time, so that the air flowed into it by the other pipe, and the vessel rose of itself to the surface. An enormous chain, each link of which weighed over two hundred pounds, was used to help lift them, when necessary, or alone when it was found most easy to use alone.

A very important use to which the submarine armor is often put, is that of enabling the diver to clean the bottom of a vessel, below water, while she is moving. This is a great convenience, as it saves the delay and expense of being obliged to place her in a dry dock. A rope ladder, with rungs of wood or iron, is stretched under the ship, passing down one side and up the other. It is thus drawn tight, and the diver descends. A bar, tied at each end with a rope, ending in a hook is hung by the hooks to the rungs, and gives him a seat, leaving his hands free. He may also fill his air-tight suit with air, and thus be partially sustained against the side of the ship. The sailors of the U.S. ship Colorado repaired, at Cherbourg, the injuries suffered by the monitor Miantonomoh, in five days, though the weather was rough. The French iron-plated ram, Taureau, had her bottom scraped and entirely cleaned of sea-weed and shells in 109 hours of labor, with a great increase of her speed.

In Mobile Bay some of the most successful diving operations have been carried on. About a sunken vessel there, it became necessary to sink a row of piles, into the bed of quicksand which had gathered round her. On trial the ordinary pile-driving machine was found incompetent to do this. Under the strokes of the falling weight the elastic sand rebounded, and the pile was thrown out. This unexpected difficulty was met in a simple, but most effective way. A suction-pump was rigged up, and the hose tied to the end of a pile; when the pile touched the bottom the pump was set to work, and the suction bored a hole in the sand, into which the pile fell with a rapidity that was startling. When the pile had been sufficiently sunk, the hose was withdrawn, and the sand settling round the pile, held it as fast as though it had been cemented in.

During the late civil war the monitor Milwaukee was struck by a concealed torpedo in Mobile harbor and sunk. During the war these torpedos sunk three of the monitors in this harbor, besides several dispatch boats, which met the same fate. The Milwaukee was sunk nearly due east from the city, and during the continuance of hostilities an effort was made to rescue her armament and her machinery. Her guns cost the Government $30,000 each. A party of divers were engaged, who were chiefly mechanics and engineers, who were exempt from military service in the Confederacy, but who sympathised fully with its cause. The duty was one of singular danger, since it had not only those peculiar to submarine diving, but as she lay within range, and hostilities still continued, the divers while below, though safe there from being hit, were yet in danger of even a worse death, from the injury which might be done to the air-pump above, upon which their supply of air depended, and which was of necessity exposed.

The work below was also peculiarly arduous. The hulk was crowded with the entangled machinery of sixteen engines, cuddies, posts, spars, levers, hatches, stanchions, floating trunks, boxes, and the confusion worse confounded by the awful, mysterious gloom of the water, which is not night or darkness, but the absence of any ray of light to touch the optic nerve. The sense of touch is the only reliance, and the life-line is the only guide of the diver. The officers and men of the ship were anxious for the recovery of their baggage, and offered the divers salvage for its rescue. One of the officers was very anxious to obtain his trunk, which was in a remote state-room, and offered fifty dollars reward for it. The diver who undertook the task has described the difficulties he encountered in its execution. To find the state-room required that he should descend below the familiar turret-chamber, through the inextricable confusion of the tangled machinery in the engine room, groping among floating and sunken objects. By touch alone he was to find a chest, to handle it in that thickening gloom, to carry it, push it, move it through that labyrinth, to a point where it could be raised, and through all this he had to carry his life-line and his air-hose. Three times the line became entangled in the machinery, and three times he had patiently to follow it up, find the place, and release it. Then the door of the state-room shut when he was in it, and round and round that little chamber he groped, in the dark, before he could find it again. All parts of the chamber seemed the same, a smooth slimy wall, glutinous with the jelly-like deposit of the sea-water. The line, entangled, became, instead of a guide, a further source of error, and the time was passing away, and life was dependent upon the continuity of the tube. There was no chance to hasten; with tedious and patient care he must follow the life-line, find its entanglements and slowly loosen them, then carefully taking up the slack follow the straightened line to the door. Nor must he forget the chest, slowly he heaves and pushes, now at the box, now at the line, which catches on every projecting knob, handle, peg or point of the machinery. Finally, however, his cool-headed patience is rewarded with success. He gets the chest to the open air and restores it to its owner; but in so doing he has made the worst mistake of all; he has mistaken the character of the man; he never paid, or offered to pay, the fifty dollars.

Another instance of cool determination in the unforeseen dangers of submarine diving occurred to a diver who was engaged in the recovery of the valuable dry dock at Pensacola Bay. In the passionate destructiveness which was so violently manifested by the South at the commencement of the civil war, as children in their rage destroy their own playthings, this structure was burned to the water's edge and sunk. Afterward a company was formed to raise it. It was built in compartments, and this method of construction, which originally was intended to prevent it from sinking, now served to prevent it from floating. Each one of the small water-tight compartments, now they were filled, kept it down. It was necessary to break into the lower side of each of them, and allow the water to flow evenly into them.

The interior of the hull was full of these boxes. Huge beams and cross-ties intersected each other at right angles, forming the frame-work of this honeycombed interior. It was necessary to break through the outside of these, and it was a most difficult and tedious job, under water. The net-work of beams was so close that the passage between barely admitted the diver's body. Into one of these holes the diver crawled. The work of tearing off the casing occupied him an hour or more, and when it was done, he thought to back out of his place. But he found he could not. The armor about his head and shoulders, acting like the barb of a hook, caught him; he could pass in, but he could not pass out. In vain attempts to twist himself out he spent so much time that the men above began to be alarmed and increased their work at the pump. The air came surging down, and swelled up his armor, so that he was more effectually caught than ever. He signalled for the pump to stop. The cock at the back of his helmet, to let the air out, was out of his reach. His only chance was to open his dress round the wrists, where the sleeves were tied. This he set out to do, but suddenly found himself affected by breathing over the air in his armor. The carbonized air began to affect him, making his mind dreamy, and inducing an intense desire to sleep. This he could overcome only by a resolute effort of his will. Meanwhile his tugging at his wrists had been successful; the air had escaped and lessened his bulk. With the energy of despair he makes one more supreme effort. It is successful, and he was drawn to the surface dazed, drowsy and only half conscious of the peril he had undergone.

These instances, however, are exceptional, and arose only from their peculiar conditions. At other times there is a pleasure in diving, thus protected; and the divers consider it, as it is, the only true way to visit the submarine world. The first sensation in descending is the sudden, bursting roar of cascades in the ears, caused by the air driven into the helmet from the air-pump. As the flexible hose has to be strong enough to bear a pressure of twenty-five to fifty pounds to the square inch, the force of the current can be estimated. The drum of the ear yields to the strong external pressure. The mouth opens involuntarily, the air rushes in the eustachian tube and strikes the drum, which snaps back to its normal state with a sharp, pistol-like crack. The strain is for a moment relieved, to be again renewed, and again relieved by the same process.

Peering through the goggle eyes of glass arranged about his helmet, the diver sees the curious, strange beauty of the world about him, not as the bather sees it, blurred and indistinct, but clearly, and in its own calm splendor. The first thought is unspeakable admiration of the miraculous beauty of everything about him. Above him is a pure golden canopy, with a rare glimmering lustrousness, something like the soft, dewy, effulgence which is seen when the sun-light breaks through an afternoon's shower. The soft delicacy of that pure straw yellow, which pervades everything, is crossed and lighted by tints and glimmering hues of accidental and complementary colors, which are indescribably elegant. The floor of the sea rises like a golden carpet inclining gently to the surface, in appearance. This is perhaps the first thing which calls attention to the fact that he is in a new medium, and that the familiar light comes altered in its nature. Looking horizontally around him a new and beautiful wealth of color is seen. It is at first a delicate blue, but it soon deepens into a rich violet. As the eye dwells upon it, it darkens to indigo, and deepens into a vivid blue-black, solid and adamantine. It is all around him, he seems encased in the solid masonry of the waters.

The transfiguration of familiar objects is curiously wonderful. The hulk of the ship seems encrusted with emerald and flossy mosses, and glittering with diamonds, gold, and all manner of precious stones. A pile of brick becomes a huge hill of crystal, decked with jewels. A ladder becomes silver, crusted with emeralds. The spars, the masts, and yards, whenever a point or angle catches the light, multiply the reflected splendor. Every shadow gives the impression of a bottomless depth. The sea seems loop-holed with cavities that pierce the solid globe. There is no gradation of perspective.

In the mouth of a great river, the light is affected with the various densities of the different media. At the proper depth, the line is clearly seen where these meet, sharply defined. The salt water sinks to the bottom, and over it flows the fresh water of the river. If this last contains much sediment, it obscures the depths like a cloud. In freshets, this becomes a total darkness. Even on a clear, sunshiny day, and in clear water, the shadow of any object in the sea is unlike any shade in the atmosphere. It throws a black curtain over what it covers, entirely obscuring it. Standing within the shadow, is like looking out from a dark tunnel; around, everything is dark, while things in the distance can be seen clearly.

The cabin of a sunken vessel is dark beyond any ordinary conception of darkness, nor do its windows, though they may be seen, alter this darkness. The distrust of his sight grows stronger in the diver with his experience. The eye is accustomed to judge of form, proportion and distance, in a thinner medium, and is continually deceived in a denser one, until experience has taught the diver how to estimate rightly the different impressions. Perhaps the most striking illustration of this difference, the diver finds in trying to drive a nail under water. If depending on sight, untaught by experience, he is sure to fail. He will instinctively strike just where the nail is not. For this reason, even the electric light below the water, does not furnish all that is wanting: the familiar medium of the upper world is wanting, and this the electric light does not supply. By practice, therefore, the diver learns to depend entirely upon the sense of touch, and with experience, becomes able to engage in works under the sea which require labor and skill, with the easy assurance of a blind man who finds his way with confidence along a crowded thoroughfare.

The conveyance of sound through water is so difficult, that under the sea has been called the world of silence. But this is not strictly correct. Some fish have the power of making sounds, and they all have simple and imperfect auditory organs. To the diver, however, save for the cascade of air through his air-pipe, the sea is silent. No shout, or word from above, reaches him. A cannon shot is dull, and muffled, and if distant, he does not hear it. A sharp, quick sound, especially if produced by striking something on the water, can be heard. The sound of driving a nail on the ship above, or a sharp tap on the diving-bell below, can be heard. Conversation between two divers, below the water, is, by the ordinary methods, impossible, but by touching their helmets together, they can converse, the vibrations being transmitted through the metallic substance, and to the air inside.

The diver has also a new revelation of the character and beauty of fish and other inhabitants of the sea when he thus meets them at home. The exudations covering them, is there a brilliant varnish. Their lustrous colors are beautiful in the fish market, but when in their native element, they are seen full of life, nimble and playful, they appear to be the most graceful creatures, and cannot be observed unmoved. The eyes of the fish are visible as far as the fish can be seen, and its whole animate existence is expressed in them. In the minnow and sun-perch there is a fearless familiarity, a social and frank intimacy with their novel visitor which surprises him. They crowd around him, curiously touch him, and regard all his movements with a frank, lively interest. Nor are the larger fish shy. The sheep-head, red and black groper, sea-trout and other well-known fish receive the diver with fearless curiosity. In their large, round eyes he reads evidence of intelligence and curious wonder, which at times is startling from its entirely human expression. No faithful dog, or pet animal could express a franker interest in its eyes.

Their curiosity is expressed, not only in their eyes, but in their movements. They share with mankind the desire to touch what is novel to them. A diver was approached by a large catfish, who came up and touched him with its cold nose. The man involuntarily threw up his hand, and struck the palm on the fish's sharp fin. There was an instant struggle before the fish wrenched itself free, and then it only swam off a short distance, staring with its black eyes at the intruder as if it wished to ask who he was, and what he wanted.

A long stay by the diver in a single place enables him to test the intelligence of the fishes who visit him. A diver, whose occupation kept him in one spot, was continually surrounded, while at work, by a school of gropers, averaging about a foot in length. Having identified one of them who had suffered from an accident, he noticed that it was a daily visitor. After they had satisfied their first curiosity, the gropers apparently decided that their novel visitor was harmless and clumsy, but useful in assisting them to get their food. They feed on crustacea and marine worms, which hide under the rocks, on mosses, and other objects on the bottom. In raising anything from the mud a dozen of these fish would thrust their heads into the hole for their food, before the diver had removed his hand. They followed him about, eying his motions, dashing in advance, or around in sport, and evidently displaying a liking for their new friend. Pleased with such unexpected familiarity, the diver brought food with him, on his return, and fed them from his hand as one feeds a flock of chickens. Sometimes two would get hold of the same morsel, and then would result a trial of strength, accompanied with much flashing and glitter of shining scales. But no matter how called off, their interest and curiosity remained with the diver. They would return, pushing their noses about him, with an apparent desire to caress him, and bob down into the treasures of worm and shell fish his labor disclosed. He became convinced that they were sportive, and indulged in play for the fun of it. This curious intimacy was continued for weeks: that they knew and expected the diver at his usual hour, was a conclusion he could not deny, since they, unless driven away by some other fish who preyed on them, were always in regular attendance during his hours of work.

The depth at which men can descend in a suit of submarine armor, has been tested by experiment with the following results: The diver can breathe, and his organs may retain their normal condition, and he preserve his presence of mind, to a depth of 130 feet, but when he exceeds this depth by ten or twenty feet, the external pressure causes physiological effects on his organs, independent of his will. One hundred and thirty feet is therefore the depth which experiment has shown to be the greatest at which any prolonged submarine work can be performed. Within this limit, security to life is perfectly compatible with an attempt to recover any ship or sunken treasure which will pay the expenses.

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