C URRENT LITE RAT IJR,E.
SCIENCE IN NUBIBITS.
Cloud Studies. By Arthur W. Clayden. (J. Murray. 12s. net.) —Coleridge in a famous sonnet remarks on the pleasures of the amateur meteorologist, who can
"With head bent low And cheek aslant see rivers flow of gold,
• Tvrixt crimson banks, and then a traveller go From mount to mount through cloudland, gorgeous land I"
Mr. Clayden gives us a very fascinating treatise on the art of studying the clouds, which shows that even more gratification than Coleridge imagined may be obtained from a scientific acquaintance with their nature. Cloud study was probably one of the earliest branches of meteorology, and yet it is still in its infancy. "Cloud observers in all ages suffer from a peculiar difficulty. They have had no common language, no code of signs by which they could benefit from the work of those who had gone before them, no means of transmitting their own experience to each other, or to those who would come after them.
• In all languages there is an extraordinary scarcity of cloud names, and such as do exist are frequently applied to quite different forms by different people. So pronounced in this lack of terms that any one who tries to describe a sky without using any of the modern scientific names finds himself obliged to rely
on long detailed descriptions, backed with references to well- known objects, whose outlines or structures resemble the clouds more or leas vaguely." A brilliant word-painter like Ruskin can achieve wonderful success in this way, but the ordinary man's attempt to describe'clouds is apt to degenerate into the vacilla- tions of Polonius. It is just about a hundred years since Howard first attempted a satisfactory classification of the clouds. He pro- posed three main types,—cirrus or fleecy clouds, stratus or sheet-like clouds, and cumulus or lumpy clouds. The great rain-clouds were distinguished by the special name of nimbus. Unfortunately there is an infinite variety of cloud forms which can be arranged in a perfectly continuous series, and Howard's classification is somewhat too limited. It has been developed into the so-called International Code, which is based not only on the appearance, but on the meteorological history of clouds. The easiest way to study clouds is by watching their reflections in a black mirror,— a thin piece of plate-glass whose back is covered with a glazed black enamel. This diminishes the brightness of the sky to such an extent that cloud-detail stands out much more clearly, whilst the painful experience of looking upwards for any length of timo is eliminated. Photography is also very helpful. Mr. Clayden's book is illustrated by a large number of very beautiful and in- structive cloud photographs, with the aid of which the reader will have no difficulty in learning to identify the typical cloud forms. This volume is essentially practical, and any one who has read it with attention will find a new interest added for the future to his daily study of the sky.
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