Since a considerable number of new terms have been suggested in the foregoing pages, it may be convenient to collect them and tabulate them, so as to show their relation to those already recognized by the International system.

In the atlas put forward by the committee, sixteen varieties are recognized by distinct names, and these are drawn up in tabular form with appropriate abbreviations for use in making records.

The names are—

During our survey of these groups we have found that some of them include clouds of many shapes, which must be due to very diverse conditions. It follows that if observations are to be made on the occurrence of these special kinds, with a view to arriving at a thorough understanding of the circumstances to which they owe their forms, it becomes necessary to devise a code of names and symbols whereby an interchange of ideas and records may be rendered possible. Specific names have been proposed as each form was considered, and it only remains to sum them up concisely. Subsequent observation, particularly in other climates, may show that further additions should be made; but if the principle of specific names be once admitted, it will be easy to fill any omission.

Group Cirrus.

Under the general head of cirrus we have found nine distinct forms—

1. Cirro-nebula (Ley) (Plates 2 and 3). Cirrus veil.

Characterized by comparative absence of structure and by the formation of halo. Ci. Na.

2. Cirro-filum (Ley) (Plate 7). Thread cirrus.

Built up of fine long threads, straight, curved, or crossing, but free from hazy curling or flocculent structures. Ci. F.

3. Cirrus excelsus (Plate 5). High cirrus.

Characterized by great altitude, thinness, irregular branching structure. Ci. Ex.

4. Cirrus ventosus (Plate 6). Windy cirrus.

Characterized by curving branches leaning forward in the direction of movement, and other long curving streamers lagging behind and below. Fluffy parts are usually present, and mark the origins of the long curling fibres. Ci. V.

5. Cirrus nebulosus (Plate 9). Hazy cirrus.

Characterized by the absence of sharply defined lines, fibres, or streamers; all parts of the cloud being hazy, and suggestive of other varieties of cirrus out of focus. Ci. Neb.

6. Cirrus caudatus (Plate 8). Tailed cirrus.

Characterized by small hazy or fluffy heads behind or below which hang long streamers, which taper away more or less to a point. The tails are sharply defined, and so are the edges of the heads. Ci. Ca.

7. Cirrus vittatus (Plates 12 and 13). Ribbon cirrus.

Characterized by formation in long bands of cloud, sometimes made of parallel long fibres with cirrus haze linking them together, sometimes consisting of a long bundle of fibres, from which others diverge at an angle as shown in the plate. Ci. Vt.

8. Cirrus inconstans (Plate 10). Change cirrus.

Characterized by a peculiar ragged, wavy appearance. It is generally only the beginning or the end of a mass of cirro-stratus or cirro-cumulus, but occasionally it vanishes shortly after its appearance, without reaching the further stage. Ci. In.

9. Cirrus communis (Plate 11). Type cirrus or common cirrus.

Characterized by short irregularly curling fibres collected together in considerable patches. No definite arrangement into any of the forms already described. Ci. Com.

Group Cirro-stratus.

Under this group the cloud usually shows some structure, being apparently built up from a massing together of detached forms at a common level. When this is so it should be described by adding the specific name of the detached form most nearly related.

1. Cirro-stratus nebulosus (Plates 3, 4, and 14). Hazy cirro-stratus.

Characterized by absence of visible structure. Ci. S. Neb.

2. Cirro-stratus communis (Plate 16). Common cirro-stratus.

Characterized by the presence of short curling fibres matted together. Ci. S. Com.

3. Cirro-stratus vittatus (Plate 57). Ribboned cirro-stratus.

Characterized by being made up of long stripes or bands of cloud. Ci. S. Vt.

4. Cirro-stratus cumulosus (Plate 17). Flocculent cirro-stratus.

Characterized by an obscurely granular structure. Ci. S. Cu.

Many forms of cirro-stratus are arranged in waves or ripples. This is indicated by attaching the word undatus, or waved, after the ordinary specific name, or the letter U after the abbreviation.

Group Cirro-cumulus. Divisible into three species.

1. Cirro-macula (Ley) (Plate 23). Speckle cloud.

Characterized by semi-transparency, by the fact that the particles are frequently whiter and more opaque on their edges. A patch of cirro-macula always looks like a thin sheet which has curdled. Ci. Ma.

2. Cirro-cumulus nebulosus (Plates 20 and 21). Hazy cirro-cumulus.

Characterized as rounded balls of semi-transparent cloud, but ill-defined and hazy. No shadows. Ci. Cu. Neb.

3. Cirro-cumulus (Plates 18 and 19).

Characterized as opaque rounded balls clearly defined, but showing no shadows on their under sides. Ci. Cu. Com.

Wave forms again are indicated by the addition of the word undatus.

Group Alto Clouds. Divisible into nine species.

1. Alto-stratus. High stratus.

A uniform veil of cloud showing no details of structure except local variation in density in patches. Rarely dense enough to completely hide the sun, or even the full moon. A. S.

2. Alto-stratus maculosus (Plate 30). Mackerel sky.

Characterized as numerous nearly equal and small lenticular patches ranged on a level and about equi-distant from each other. A. S. Mac.

3. Alto-stratus fractus (Plate 34).

Patches and bits of cloud of irregular shape, but resembling broken bits of a level sheet. A. S. Fr.

4. Alto-strato-cumulus (Plate 32).

Intermediate between alto-stratus and alto-cumulus. A. S. Cu.

5. Alto-cumulus informis (Plate 25).

Characterized as more or less rounded cloudlets interspersed with ragged bits of cloud and occasionally with streaks of cirrus, the cloudlets showing no clear-cut outlines, but having distinct shadows. A. Cu. In.

6. Alto-cumulus nebulosus (Plate 26).

Hazy alto-cumulus. A. Cu. Neb.

7. Alto-cumulus castellatus (Plate 28). Turret cloud.

A high cloud resembling a number of tall narrow cumulus clouds on a very diminutive scale. The cloudlets show distinct shadows, are very opaque, and their upper margins are sharply defined. Vertical axes longer than the horizontal ones. A. Cu. Ca.

8. Alto-cumulus glomeratus (Plate 29).

Characterized by the roundness and regularity of the cloudlets, which have sharp margins, cast distinct shadows, and have their axes about equal in all directions. A. Cu. Gl.

9. Alto-cumulus communis.

Small high cumulus of the ordinary pyramidal pattern. A. Cu. Com.

10. Alto-cumulus stratiformis (Plate 27).

Flattened cloudlets gathering into small detached sheets. A. Cu. S.

Lower clouds. Group Stratus.

1. Stratus communis (Plates 37 and 41).

In its most typical state, stratus consists of a sheet of cloud of approximately uniform thickness. The most common form, however, does vary considerably, though usually dense enough to hide the sun. Portions of such a sheet would take the same specific name, unless the portions are very small and ragged, which would be expressed by adding the word fractus. S. Com.

2. Stratus maculosus (Plate 40).

Formed either by the appearance of cloud in lumps, which are always lenticular in shape, and ultimately join together to form a stratus, or by the break up of the typical stratus. S. Mac.

3. Stratus radius (Plate 42). Roll cloud.

Formed during the break up of a low stratus, which separates up into a number of parallel lines of cloud. S. R.

4. Stratus lenticularis (Plate 47). Fall cloud.

Formed by the collapse of cumulus or strato-cumulus. A cloud of evening, easily recognized as lenticular patches. S. L.

5. Strato-cumulus (Plates 38 and 39).

A term applied to either a stratus which has thickened every here and there into cumulus, or a number of cumulus which have joined together so as to show a nearly continuous common base. S. Cu.

Group Cumulus.

1. Cumulus minor (Plate 43). Small cumulus.

Cumulus clouds so small as to present the appearance of rounded lumps, no definite pyramidal form or flattened base. Cu. Mi.

2. Cumulus major (Plates 44 and 45). Large cumulus.

Characterized by a flattened base and rounded clear-cut upper surfaces. Cu. Ma.

3. Cumulo-nimbus (Plates 49 to 52). Storm cloud.

Characterized by the expanded, anvil-shaped, or disc-shaped top, cirrifying at its edges.

General Terms

Nimbus, a term applied to a cloud from which rain is falling. When the form of the cloud is visible, the term should be attached to that belonging to the cloud. It may, however, be used as a substantive alone when there is nothing to show from what sort of cloud, or combination of clouds, the rain is falling (Plates 35 and 36).

Nimbus is either heavy stratus, massive strato-cumulus, or a combination of these with stratiform clouds above, and possibly ragged masses of fracto-cumulus below. N. either alone or after the sign of the cloud.

Fracto- is a term placed as a prefix before the name of a cloud to indicate that the cloud has ragged irregular margins, as if it had been more or less torn to pieces. It is sometimes less awkward to append the word fractus after the name of the cloud.

A convenient abbreviation would be to write F. after the name of the cloud.

Undatus, or waved, should always be added to the name of any cloud which shows the arrangement so described.