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vapour arising from flats and sandbanks gives a hazy and delicate 
effect to the light, very suggestive in a picture. 
With regard to these differences of atmospheric effect caused 
by change of locality, it appears that such change is found rather 
in the grouping, elevation, and effects of light and colour, than 
in the forms themselves, though there are certain forms, no 
doubt, perfectly local, especially in mountainous districts. These 
generally owe their origin to geographical configuration ; and 
their study lies as much within the province of the physical 
geographer as that of the meteorologist. In passing, however, I 
may remark that the curious disc or cap which is seen near the 
peak of some mountains, and which maintains its form in a 
breeze of wind, must have its particles in rapid motion ; being- 
caused by the continuous impact of vapour currents upon a 
colder stratum, which determines condensation and visibility. 
This is a good example of the principle stated above, that iden- 
tity of visible form at two different moments is no proof of 
continuity of composition. The flame of a candle, which cannot, 
chemically, remain the same two moments together, affords 
another illustration of this. A cloud, like the human body, may 
often be likened to an eddy. Physiology teaches us that the 
body is sustained by a constant motion of particles drawn in 
from external sources and passed off again after undergoing a 
change of form ; yet no one doubts his possessing the same body 
which he had, say, ten years ago. The saying, that 66 sameness ” 
must not be confounded with 66 this-ness ” and 66 that-ness,” or 
identity , in its strictest sense, is applicable in both cases. Every 
cloud, as has been remarked by Espy, is either a forming or a 
dissolving one ; but I think we may extend this, and say that 
some clouds are both “ forming ” and “ dissolving ” at the same 
time : e.g., cirro-cumulus forming from cirrus and melting into 
nimbus. 
But we now pass on to consider a form of cumulus which is 
associated with very wet weather, and which I do not think has 
yet had a distinguishing title accorded to it. This I propose to- 
call the “ high-rain ” cumulus. It is not a common species, and 
is mostly seen in autumn and spring. It deserves the name that 
I have given it, on account of the tremendously heavy showers 
that attend its appearance and the great elevation which it 
often attains. Unlike most forms of cumulus, which it is best 
to observe when somewhat near the horizon, so that the vertex 
may be seen in outline, this cloud reveals its characteristics 
best when almost overhead. Let the reader picture to himself 
a mild, muggy day in spring or autumn, everything soaking 
with recent showers, with heavy, lumpy-looking cumulus hanging 
about the horizon, and a drift of flattish, irregular cirro-cumulus 
