July 26, 1894] 



NA TV RE 



293 



metre of ice thickness per annum. It is singulir that 

 an increase in the southern ice-cap tends to increase that 

 of the northern also, by lowering the level of the ocean, 

 and so retarding circulation. Any cause which lessened 

 the Antarctic ice-cap would moderate the rigour of the 

 extreme northern climate, and tend to warm the .Arctic 

 Ocean. 



So much for the first half of the book under review. 

 The remaining half will be treated in another article. 



Oliver J. Lodge. 



ELEMENTARY METEOROLOGY. 

 Elementary Meteorology. By William Morris Davis, 

 Professor of Physical Geography in Harvard College. 

 (Boston, U.S.A. : Ginn and Co., 1894.) 



THE necessity for the production of text-books would 

 seem to diminish with lapse of time, but the 

 examination of publishers' catalogues discloses no 

 diminution in their numbers. If there be any excuse for 

 the writing of new text-books in any branch of science, 

 it might be found in those at present unformed depart- 

 ments, like meteorology, where well-directed and syste- 

 matic inquiry is constantly enlarging the boundaries of 

 knowledge by the addition of new facts, or the discovery of 

 fresh grounds for the acceptance of facts not yet admitted 

 as demonstrated truths. The science of meteorology is 

 not like that of mathematics, which immediately displays 

 its power, and has nothing to hope or fear from passing 

 time ; but appealing as it does to observation and ex- 

 perience, its progress must be gradual and comparative. 

 And if any one be entitled to write text-books, it is those 

 who having been engaged practically in teaching have 

 felt a particular want to be ill-supplied, and who feel 

 themselves qualified by their office and minute acquaint- 

 ance with the subject to remedy the defect. For these 

 reasons we may w'elcome the appearance of Prof. Davis' 

 work on "Elementary Meteorology,' which originally 

 intended for those engaged in the earlier years of college 

 study, and with whom the author has been brought much 

 into contact, may well be read by others, who wish to 

 keep themselves acquainted with the more recently- 

 acquired facts concerning the behaviour and the pro- 

 cesses of atmospheric circulation, in fact. Prof. Davis 

 has had both classes of readers in his mind, as he has 

 prepared this work ; and further,, recognising how many 

 in his own country are more or less intimately connected 

 with the national and state weather services, he has 

 endeavoured to supply them with a well-digested treatise 

 which may be a supplement to the meagre but precise 

 instructions issued to observers under official authority. 

 It is not to a text-book of this character that one goes 

 to learn the present position of the more speculative side 

 of meteorology, and since the author excludes from his 

 programme purely mathematical discussion, some of the 

 more recondite inquiries cannot be treated. The quali- 

 ties that we should look for in a book intended primarily 

 for college students, are exactness of facts and expression, 

 lucidity of description, and orderly consecutive arrange- 

 ment, carrying the student gradually forward to complete 

 knowledge of the subject, within the limits proposed by 

 the author. And, supposing this to have been the aim 

 NO. I 29 I, VOL. 50] 



of the writer, it seems to have been admirably fulfilled. 

 A text-book embracing the views and the experience of 

 others cannot hope to be original, but it should be 

 thorough, and this on the whole is the opinion we have 

 conceived of the book. 



In a few short chapters, we have a description of the 

 atmosphere as a whole, and of the forces that are con- 

 tinually operative, giving rise, by the succession of day and 

 night and summer and winter, to vertical interchanging 

 currents whose behaviour under varying conditions and 

 circumstances embraces the whole province of meteoro- 

 logy. Having thus prepared the way by sufficient refer- 

 ence to the physical processes which influence the tem- 

 perature of the earth as a whole, it might have been ex- 

 pected that the author would have proceeded naturally to 

 the consideration of local temperatures, and a more minute 

 division of his subject. But, unfortunately, he delays the 

 progress by the introduction of a chapter on the colour of 

 the sky. Doubtless the author can defend himself, but 

 to us, it appears an interruption of the orderly develop- 

 ment of the subject, and a defect in the arrangement 

 of the work. It is, however, the only distinct blemish to 

 which we shall have to refer in the plan and conception 

 of the book. We should suspect that the subject of the 

 colour of the sky has had great attraction for Prof. 

 Davis, and that he has over-valued its importance in a 

 book of this nature. But having surmounted that diffi- 

 culty, there is nothing to stop the consideration of tem- 

 perature, its measurement, its distribution, and the 

 causes affecting its disturbance, either as a whole by 

 the obliquity of the earth's axis, or locally as by ocean 

 currents, &c. All this is very admirably arranged ; and 

 here we may say a word for the sufficiency and clearness 

 of the diagrams. Prof. Davis has apparently had access 

 to a very admirable and complete collection, and his 

 selections are judicious and well illustrative of the points 

 under discussion. 



From isotherms the transition to isobars is easy and 

 natural, and though we cannot expect anything original 

 in the description of a barometer, the quality of thorough- 

 ness to which we have before alluded is again illustrated. 

 The author does not recommend the correction of the 

 individual readings of the barometer to the sea-level, a 

 practice which is falling more and more into disuse. Un- 

 fortunately a definition of sea-level, as understood in 

 .\merica, is not given, at least where we expected to find 

 it. We doubt whether many English readers could 

 supply a correct definition, but the expression may be 

 perfectly clear on the other side of the .'Vtlantic. 



Proceeding as far as possible with the discussion of 

 barometric readings, revealing the varying distribution 

 of pressures, the author finds it necessary to introduce 

 the subject of the observation and distribution of the 

 winds. This we consider absolutely in its right place, 

 and assists the gradual progress materially. On the 

 subject of the reduction of wind observations the informa- 

 tion is certainly meagre. Wind observations offer one of 

 the most complicated problems in meteorology, one cer- 

 tainly out of the range of the ordinary college student, 

 and this may be a sufficient apology for the author. 

 Here, too, we should have looked for some reference to 

 the recent work of Prof. Langley, indicative of both the 

 difficulty of making exact observations of velocity, and 



