The Laws of the Winds prevailing in Western Europe

Abstract

EVEN when we differ from an author's conclusions, the work of one who shows himself an honest and capable inquirer has a just claim to our attention. Mr. Ley evidently writes from practical knowledge of his subject, and his assiduity in collecting and charting observations must have entailed on him an amount of labour which only those who have been engaged in similar work can thoroughly understand. Unfortunately, as it appears to us, he has confined his investigations almost entirely to the limits set forth on his title-page; and the winds of Western Europe, though highly suggestive and subject to more exact observation than any others except those of the United States, are by no means to be taken as representative. Mr. Ley has taken them as such, and has thus laid down a series of general propositions, which may be briefly summed up in one—that revolving storms are caused by the barometric depression consequent on heavy rain over a large area. He brings forward some curious home instances in illustration of this; but looking farther afield, on the slopes of the Himalayas—to mention only one locality—a much heavier and longer continued precipitation than any he has instanced takes place every summer, and does probably cause a very great depression of the barometer, but certainly does not give rise to any winds such as he has described. On the hills of Khasia, again, where the unparalleled rainfall is as much as from 30 to 40 inches a day for days together, and puts the paltry ½ or 3/4 of an inch a day of Mr. Ley's examples almost beyond the pale of comparison, no such storms are generated. In the same way, the explanation of the eastward direction which these barometric depressions take in our latitudes, which differs only in its greater detail from that given by Prof. Mohn in the “Storm Atlas,” is applicable only to temperate latitudes; the westward advance of tropical cyclones cannot be referred to it; and it seems to us improbable in the extreme that the course of a storm is regulated by one law in one part of the world, and by a totally distinct law in another. Besides this, in the detailed application of the law which he deduces for Western Europe, the author appears to fall into the mistake of attributing the rainfall of mountain districts to the mere contact of the moist air with the cold mountain slope; that this is not the case—that it is due rather to the hoist into the upper regions which the air receives on impinging against the slope—is curiously shown by the fact that, when the hills are not high, most rain falls on the lee side. One familiar instance of this will illustrate our meaning. The gauge which in all England shows the greatest rainfall is at Stockley Bridge, just above Seathwaite; it is distinctly under the lee of the ridge which joins Great Gable to Great End, and separates Wastdale from Borrowdale. The mist, blown in from seaward, fills Wastdale, and is lifted up the slope of this ridge (Stye Head Pass). Crossing over out of Wastdale, the mist curling up the hill is frequently so thick that the path cannot be seen 10 feet in advance; but immediately on reaching Stye Head Tarn the mist vanishes, to fall as rain over Seathwaite. But altogether, though we admit neither the author's premises nor his conclusions, his work is none the less highly interesting. It does not contain much that is new, but it discusses and illustrates the theories of Mohn and Buchan in greater detail than has yet been attempted. We would, however, decidedly object to the ex cathedrâ tone which is occasionally adopted. In empirical science very little is “obvious,” and perhaps nothing is a “truism;” certainly the influence attributed to the earth's rotation is neither one nor the other, for it is denied, disputed, and doubted by very many capable meteorologists.

The Laws of the Winds prevailing in Western Europe.

By W. Clement Ley. Part I. (Stanford, 1872.)