426 



NATURE 



[February ii, 1909 



Dr. Barton has copied Lord Rayleigh in concluding 

 with a section on electrical oscillations. We have 

 never quite understood why this subject should be 

 treated so fully in a text-book on sound. Some know- 

 ledge is, of course, needed in connection with the 

 electrical maintenance of vibrations ; but the know- 

 ledge so required is very much more than supplied by 

 the theorems given here. 



There are twenty-three pages of questions at the 

 end. There are very few misprints in the entire 

 book. We notice modulus spelt wrongly twice on 

 p. 131, and we believe that it is to W. Konig, not A. 

 Konig, that the explanation of the striated appear- 

 ance of the dust in a Kundt's tube should be attributed. 



(2) The second book which heads this review is a 

 French translation of a Russian text-book. The 

 German translation of the same portion was reviewed 

 by us some time ago, and consequently a very brief 

 notice will now suffice. To the present translation 

 there is a preface by Amagat, and to the eulogistic 

 remarks which he makes on Chwolson's treatise we 

 would add that we consider the entire text-book to 

 be the most satisfactory and complete of anv with 

 which we have met. The present part is, perhaps, 

 not the most striking in its superiority; that praise 

 must be reserved for the volume on heat and thermo- 

 dynamics; but the critical judgment which Chwolson 

 everywhere exhibits has enabled him to deal with the 

 subject of sound in a very masterly way. 



OUR BOOK SHELF. 

 The Zonahhclt Hypothesis. .4 New Explanation of 



the Cause of the Ice Ages. By Joseph T. Wheeler. 



Pp. 402. (Philadelphia and London : J. B. Lippin- 



cott Co., 1908.) Price 2.50 dollars net. 

 The author of this book has read widely, and the 

 latter two-thirds of it, dealing with comparative 

 mythology, may be useful on account of the quota- 

 tions. The first third is, as Mr. Wheeler shows in his 

 historical introduction, a development of an idea sug- 

 gested by Tyndall and by several later authors, to the 

 effect that a thin " canopy " of a gas, capable of 

 transmitting the luminous heat of the sun, but im- 

 pervious to the dark heat-rays radiated back from the 

 earth, might have a profound effect on the general 

 climate. Such canopies may have arisen from time 

 to time through the fall of rings of matter external to 

 the atmosphere. 



The author prefers to regard these rings as 

 planetesimal in origin, and the new point introduced 

 by him is the possibility that the canopies were re- 

 solved into belts, thus permitting of strong climatic 

 zones. It is presumed that each ring, as it approached 

 the earth, would divide and spread away as canopies 

 towards both poles, where the centrifugal force was 

 least. Such a time would be a generally warm one, 

 with the production of clouds from evaporated water. 

 These clouds would occur in high levels of the atmo- 

 sphere, and would assist the rise of temperature. As 

 the canopy aged and became unstable at its edges, it 

 moved back towards the equator, leaving " natural 

 sun-controlled climatic conditions," i.e. colder ones, 

 in its wake (p. 103). The regions under the canopy 

 would remain cloudy and warm. Condensation now 

 took place in " the middle ground between the pole 

 and the canopy belt." Here we have all that is needed 

 for the production of a glacial period. Fluctuations in 



NO. 2050, VOL. 79] 



the position of the edges of the canopy would account 

 for interglacial episodes. The final breaking up of the 

 planetesimal belt, and the disappearance of the accom- 

 panying atmospheric cloud-belt, caused the glaciation 

 to invade the whole earth (p. 114). Primitive man 

 saw the latest cloud-belts, which originated the myths 

 of serpents twined about the earth. 



The gases or planetesimal materials of each original 

 belt are held to have been ultimately deposited as 

 cosmic dust over the globe, after the manner of Mr. 

 H. L. Fairchild's primitive " cosmoclastics " (p. 44). 

 " As a canopy fell a geological age ended, and with 

 it its life conditions " (p. 52). A large number of facts 

 are called in to support the hypothesis, and even the 

 size of Carboniferous insects is said to be an indication 

 of a denser atmosphere. When it is suggested (p. 45) 

 that the earth that has accumulated round the ruins 

 of Nippur " may be in part the wind-blown remnants 

 of cosmical world chaff," we feel inclined to appeal 

 to geologv rather than speculation ; and it is with 

 this feeling that wo lay down the volume. One of 

 the best things in the unfolding of Mr. Wheeler's hypo- 

 thesis is the prominence given to the idea that tropical 

 heat is quite compatible with an atmosphere of cloudy 

 darkness. G. A. J. C. 



A Monograph of the British Desmidiaceae. By W. 



West and Dr. G. S. West. Vol. iii. Pp. xv+274; 



31 plates (Ixv.-xcv., of which 14 coloured). 



Si.xtv-fifth year of issue. (London : Printed for 



the Ray Society, 1908.) Price 255. net. 

 In notices of the earlier volumes we have had 

 occasion to speak very highly of this work, which 

 deservedly takes a front rank among monographs 

 devoted to a single family of plants. The merits so 

 conspicuous in these volumes are equally so in this, 

 which is devoted entirely to a part of the great genus 

 Cosmarium. Beginning with species 51, the text 

 closes with species 224 ; but seven additional species 

 are figured, although exigencies of space require their 

 descriptions to be held over to vol. iv. A very large 

 number of the species have named forms or varie- 

 ties under them. A considerable proportion of these,, 

 and a few of the species, are new to science. The 

 references to the literature under each already known 

 species and variety are very ample. In discussing the 

 distribution of each, the authors are careful to ac- 

 knowledge the work of others, the names of Roy 

 and Bissett occurring very frequently, and Archer, 

 Cooke, Ralf, and Wills on many pages ; but the 

 larger part of the whole is the result of the very 

 extensive researches among fresh-water algae carried 

 out by the authors themselves in many parts of the 

 British Islands. The distribution beyond our islands 

 is also given, and for some species is extraordinarily 

 wide, e.g. C. venustum extends over the northern 

 hemisphere, and has also been found in Java, 

 Australia, and Paraguay, and several others are also 

 dispersed in the fresh waters of almost every part 

 of the world where desmids have been sought for. 

 Under most of the species important notes direct 

 attention to the more distinctive characters, the rela- 

 tions to allied forms, whether British or from other 

 countries, peculiarities of habitat, and other character- 

 istics that cannot be introduced into a systematic 

 description, but which are often exceedingly helpful. 



Every species and almost every variety and 

 " form " are figured in the plates, wherever possible 

 in positions to show the forms and markings or 

 sculpture from the different aspects required to give 

 a true conception of these characters. The details 

 of the cell-wall are alwavs shown in uncoloured, and 

 usunllv the anoearnnce of the living cells in coloured 

 figures, all alike being the work of Dr. G. S. West. 



