384 
and snow-clouds of aqueous vapour. Where there is no proof 
of the existence of Howard’s third type, being that, according to 
this savant, it is a mist which overspreads the earth at sunset, 
but which is raised in the morning at the first appearance of that 
luminary. As to number, my nomenclature offers the same de- 
termination of cloud forms, that is to say, seven—the two types 
and five derivatives. 
The order in which the clouds are placed in my table corre- 
spond, at the same time, to the order of their appearance, from 
the highest region of the Cirrus down to those nearest the earth, 
where the Fracto-cumulus are produced, according as the vapour 
of water passes from the state of frozen particles to that of aque- 
ous vesicles, or vice versa. However, the Pallio-cumulus, which 
serves as a transition between the two types and their derivatives, 
is found a little more elevated than the Cumulus. 
I have thought it suitable to modify Forster's vulgar nomencla- 
ture by substituting other names more in harmony with the form 
and nature of the clouds. I give in continuation the old and 
new classification : 
Poey’s Nomenclature 
. Curl-cloud 
. Thread-cloud 
. Curdled-cloud 
. Sheet-cloud 
Forster’s Nomenclature 
Woe emer 6 QO Ur=clOud-aG ss 
Cirro-stratus . . . Wane-Cloud. . . 
Cirro-cumulus . . Sonder-cloud. . . 
Pallio-cirrus .... 
Cumulus. . . Stacken-cloud . . . Mount-cloud 
Pallio-cumulus. ............ Rain-cloud 
Fracto-cumulus .......... .. Wind-cloud 
Cirrus 
With the exception of Cirrus, whose name, ‘‘ Curl-cloud,” ap- 
proaches nearest the form of this species of cloud, all the deter- 
minations have beon changed. The Pallio-cumulus replaces the 
Nimbus, also named ‘‘ Rain-cloud.” 
I.—CIRRUS (HOWARD). 
Cirrus, so named by Howard (‘‘the cat’s tail,” of sailors), 
are composed of filaments, whose evsemble resembles sometimes 
a curled hair, a twisted tuft, plumage, the flowing tail of a horse, 
at other times they are disposed in long, straight bands parallel 
to each other, or divergent palmated, or like a fish bone or 
vertebral column, their greater axis being oriented according to 
the sailing of the cloud and the direction of the wind existing at 
that altitude, which is not slow in making itself felt on the earth, 
When they form two or more systems of straight parallel bands, 
by an effect of perspective, they appear to diverge from their 
point of departure at the horizon and to converge toward the 
point of the horizon diametrically opposite, as do the rays of the 
rising or setting sun. 
The Cirrus have always a whiteness, sometimes brilliant, 
sometimes pearly dull. The earliest and the latest reflections of 
the solar rays upon the clouds colour them with a charming rose 
tint, more or less intense, according to their density. Their pro- 
pagation is excessively slow, and their altitude is not less than 
10,coo metres (more than six and a quarter miles). These 
clouds are the highest, slowest, most rarified, most variable in 
their forms, and the most extended. The appearance and disap- 
pearance of Cirrus proclaim simultaneously the end and the 
commencement of good weather. The barometer sinks and 
then rises, the evsev2b/e of meteorological accompanying pheno- 
mena pursuing the same course. We quote from Howard : 
“They are first indicated by a few threads pencilled, as it 
were, on the sky. These increase in length, and new ones are 
in the meantime added to them. Often the first formed threads 
serve as stems to support numerous branches, which in their turn 
give rise to others. 
© The increase is sometimes perfectly indeterminate ; at others 
it has a very decided direction. Thus the first few threads being 
once formed, the remainder shall be propagated in one or more 
directions laterally, or obliquely upward or downward, the direc- 
tion being often the same in a great number of clouds, visible at 
the same time: for the oblique descending tufts appear to con- 
verge toward a point in the horizon, and the long straight streaks 
to meet in opposite points therein, which is the optical effect of 
parallel extension, The upward direction of the fibres or tufts 
of this cloud is found to be a decided indication of the decompo- 
sition of vapour preceding azz ; the downward as decidedly in- 
dicates evaporation and fair weather. In each case they point 
toward the place of the electricity which is evolved at the time. 
“Their duration 1s uncertain, varying from a few minutes 
after the first appearance to an extent of many hours and even 
days. It is long when they appear_alone and at great heights, 
NATURE 
[Sepz. 8, 1870 
and shorter when they are formed lower and in the vicinity of 
other clouds. 
“‘This modification, although in appearance almost motion- 
less, is intimately connected with the variable motions of the at- 
mosphere. Considering that clouds of this kind have long been 
deemed a prognostic of wind, it is extraordinary that the nature 
of this connection should not have been more studied, as the 
knowledge of it might have been productive of useful results. 
“In fair weather, with light, variable breezes, the sky is 
seldom quite clear of small groups of the oblique Cirrus, which 
frequently come on from the leeward, and the direction of their 
increase is to windward. Continued wet weather is attended 
with horizontal sheets of this cloud, which subside quickly and 
pass into the Cirro-stratus. 
“ Before storms they appear lower and darker, and usually in 
the quarter opposite to that from which the storm arises. Steady 
high winds are also preceded and attended by streaks running 
across the sky in the direction they blow in.” 
II. —CIRRO-STRATUS. 
Thread-cloud.—Woward’s Cirro-stratus is distinguished from 
the pure Cirrus by its filaments being smaller, more compact, 
more ramified, and, so to say, completely stratified. They are 
lower, more dense, for often the sun’s rays pierce them with 
difficulty. Their whitish tint is clearer, and it also becomes rose 
colour in similar circumstances. Their motion is a little more 
rapid. When at the horizon, we only seeing the vertical projec- 
tion, they take the appearance of a long and very narrow band. 
Tloward says : 
“*This cloud appears to result from subsidence of the fibres of 
the Cirrus to a horizontal position, at the same time that they 
approach each other laterally. The form and relative posi- 
tion, when seen in the distance, frequently give the idea of shoals 
of fish. Yet in this, as in other instances, the s¢ractae must be 
attended to rather than the form, which varies much, presenting 
at times the appearance of parallel bars, or interwoven streaks 
like the grain of polished wood. It is thick in the middle, and 
extennated towards the edge. The distinct appearance of a 
Cirrus, however, does not always precede the production of this 
and the last modification. 
“The Cirro-stratus precedes wind and rain, the near or dis- 
tant approach of which may sometimes be estimated from its 
greater or less abundance and permanence. It is almost always 
to be seen in the intervals of storms. Sometimes this and the 
Cirro-cumulus appear together in the sky, and even alternate 
with each other in the same cloud, when the different evolutions 
which ensue are a curious spectacle ; and a judgment may be 
formed of the weather likely to ensue by observing which modi- 
fication prevails at last. The C7iro-stratus is the modification 
which most frequently exhibits the phenomena of the Solar and 
Lunar halo, and (as supposed from a few observations, the Parhe- 
lion and Paraselene also. Hence, the reason of the prognostic 
of foul weather—commonly drawn from the appearance of Halo. 
The frequent appearance of Halo in this cloud may be attributed 
to its possessing great extent, at such times, with little perpen- 
dicular depth, and the requisite continuity of substance. 
‘This modification is, on this account, more peculiarly worthy 
of investigation.” 
TII.—CIRRO-CUMULUS, 
Curdled Cloud.—It is sufficient that the Cr70-stratis sink a 
little, or that the temperature of the region they occupy be 
slightly elevated, in order that the frozen aiglets may be reduced 
to snow, and give birth in consequence to Howard’s Cirro-cumu- 
Jus. In the first place the axes of the s¢v7@ grow round; then, 
by degrees, the entire stratification becomes so, until it forms 
little balls or corded cotton which we call ‘* frizzled” clouds of 
““curled” sky (in French, oztonnes or pommele,) when it is 
completely covered; in Spanish, cielo empedrado. On the 
contrary, if the C7rro-cumulus are elevated a little, or if the 
temperature is lowered, they return to the superior type of C77ro- 
stratus. The little balls of snow are congealed and crystallised 
anew into aiglets. 
The Cirro-cumulus are more dense and lower than the Cirro- 
stratus, from which they are derived, although generally the 
edges of the small agglomerations or of the entire mass of cloud 
is transformed into Cz7ro-stratus, whenever, by a greater eléva- 
tion or a lower temperature, the congélation is more vigorous. 
Their motion is also more rapid, their colour slightly greyish, 
and they may, moreover, be tinged rose-colour, or, rather, be- 
come reddish. 
