304 



NATURE 



[Ski'Temeek 9, 1909 



ology properly so-called, while parts iii. and iv. will 

 be devoted to the exposition of special questions and 

 to the principles and use of instruments. A glance at 

 the first volume of Klossovsky's " Meteorology " shows 

 at once that it is the outcome of a long and useful 

 career. In fact, the first meteorological labours of 

 the author date from the year 1882, and from that 

 time Klossovsky has not ceased to devote all his efforts 

 to teaching at the Odessa University, and to the or- 

 ganisation and direction of the network of meteor- 

 ological stations in the south of Russia. 



Klossovsky's manual, far from being simply a work 

 of compilation — the most complete of any now extant 

 — is distinguished by its originality and by the wealth 

 of the author's critical views. In many parts of the 

 work we meet with pages where certain connections 

 between meteorological data and those of other 

 sciences are admirably described; e.g. at p. 179 and 

 following pages the calorific economy of the human 

 body is discussed. Further, original observations are 

 met with for the first time; thus, at p. 273, the results 

 of the actinometric observations made by Savelieff at 

 Kiev. Again, the whole chapters devoted to solar 

 radiation and to the study of earth temperature are 

 interesting to read. 



In no other treatise are the questions relating to 

 underground temperature expounded in so complete 

 a manner. The discussion of the results of the 

 author's observations on the temperature at different 

 depths in soil covered with grass and otherwise is 

 especially noteworthy. On p. 334 there is a table 

 giving for each month of the year the temperature 

 at depths of o'6o m. and 120 m. in forest and field 

 adjoining. The forest diminishes the annual ampli- 

 tude; the differences (field — forest) are +30° C. and 

 -)-2'7° for the means of July, -04° at a depth of 

 60 cm. and — 02° at r2o m. in January. 



One of the characteristics of Klossovsky's work 

 is the care with which the most recent advances have 

 been taken into consideration; e.g. at p. 512 observa- 

 tions made in January, 1907, are noted, and at p. 606 

 the results of unmanned balloon ascents at Uccle up 

 to April II, 1907, are included. The titles of the 

 chapters in this first volume are : — Composition of the 

 atmosphere ; physical properties ; water in the atmo- 

 sphere; the oceans; solar radiation ; terrestrial radia- 

 tion ; earth temperature ; increase of heat with depth ; 

 ocean temperatures ; temperature of the lower strata 

 of the atmosphere; atmospheric pressure; formation 

 of hydrometeors ; temperature and pressure in the 

 upper atmosphere; abnormal departures. H. A. 



An Introduction to the Study of Integral Equations. 

 (Cambridge Tracts in Mathematics and Mathemati- 

 cal Physics.) By M. B6cher. Pp. vi-(-72. (Cam- 

 bridge : University Press, 1909.) Price 2^. 6d. net. 



One main problem discussed in this tract is the follow- 

 ing : let /(.\-) and K(x-, ^) be known functions, it is 

 required to determine the function u{x) so as to satisfy 

 the equation 



/.(.r)=/W + //(-^,l)«(^yi- 



Prof. Bocher shows, mainly after Fredholm, that under 

 certain conditions of a very general kind, a solution 

 exists, and may actually be put into the explicit 

 form 



.' (I 

 where D is a determinate function of a, b, and D(.v, |) 

 a determinate function of a, b, x, f. That it should 

 be possible to prove this in a simple, and at the same 

 time rigorous manner is a good illustration of the 

 NO. 2080, VOL. 81] 



increasing power of modern function-theory. Prof. 

 Bocher's exposition is very good ; he begins by a 

 heuristic discussion, which in a way resembles the 

 ordinary method of successive approximations. Having 

 thus been led to a certain expression as a presumptive 

 solution, he proceeds to verify the fact that it is one. 



Other workers in the same field who receive due 

 attention are Abel, Liouville, Hilbert, Schmidt, and 

 V'olterra ; and there are various subsidiary or supple- 

 mentary articles of great interest. 



As No. 10 of the " Cambridge Tracts in Mathe- 

 matics and Mathematical Physics," Prof. B6cher's 

 work thoroughly helps to fulfil the object of the 

 series; it is brief, self-contained, and stimulating, 

 while giving sufficient reference to original sources. 



The Scaly-iiiinged. A Book on Butterflies and Moths 

 for Beginners. By R. B. Henderson. Pp. xii + 

 115. (London : Christophers, n.d.) Price js. net. 



The study of entomology is always extending its 

 range, as shown by the numerous books which con- 

 tinue to be published especially relating to the order 

 Lepidoptera, or butterflies and moths, which always 

 seems to be the most popular of all, probably because 

 many insects included in it are attractive in appear- 

 ance, and easy to collect. ' The study is pursued sys- 

 tematically in several of our great public schools, and 

 Mr. Henderson informs us in his preface that " the 

 entomological, like most of the other sections of the 

 Natural History Society of Rugby School, is entered 

 by examination," and that as he did not find a suit- 

 able book for beginners to use in preparation for such 

 an examination, he has compiled one for the purpose. 

 The various chapters deal with insects in general, 

 and the .Scaly-Winged in particular; metamorphosis; 

 Psyche (imago) ; the Sister States (difference between 

 butterflies and moths) ; bionomics : the place of Lepi- 

 doptera in the scheme of nature; the museum; ap- 

 pendix: note on the vision of insects; and list of 

 some useful books for consultation, Furneaux's 

 " Butterflies and Moths " being specially recom- 

 mended. There are twentv-two useful text-illustra- 

 tions of structure and apparatus, and the instructions 

 for collecting and preservation in the chapter on the 

 museum are particularly good. 



Fossil Plants. Sixty Photographs illustrating the 

 Flora of the Coal-measures. Bv E. A. Newell Arber. 

 Pp. 75. Gowans's Nature Books, No. 21. (London : 

 Gowans and Gray, Ltd, 1909.) Price 6d. net. 



It is not often that anything has been done to popu- 

 larise the study of the plants of the past, a subject 

 of which the " educated layman " is, as a rule, pro- 

 foundly ignorant. This neat little volume, with its 

 beautiful photographic illustrations of some of the 

 most important coal-plants (club-mosses, ferns and 

 fern-like seed-plants, horsetails, sphenophylls, and 

 early gymnosperms) is well calculated to rouse an 

 interest in the flora of so many million years ago. 

 The great majority of the photographs are from casts 

 and impressions, showing the external aspect of the 

 fossils, and these are all admirable; we have never 

 seen a better collection. Some of the few microphoto- 

 giaphs of sections, illustrating the internal structure, 

 are equally good, though in one or two cases clearer 

 examples might have been selected. The short ex- 

 planatory notes (scarcely a dozen pages in all) are, as 

 the name of the author guarantees, thoroughly sound 

 and up to date ; they are just enough to whet the 

 reader's appetite for more, which is all that can be 

 expected or desired of a si.xpenny nature picture-book. 



