Supplement to ''Nature," March 5, 1908 



ill this country tew developments have been made. 

 Mon- attention has been given probably in England 

 to the binocular microscope than to any other form 

 Oi stereoscopic instrument. Quite recently Theodore 

 Brown has experimented with a method of monocular 

 bio-stereoscopic projection, which will doubtless one 

 day be perfected and become widely known. But 

 only his earlier work is mentioned by von Rohr, w-ho 

 does not carry his account beyond 1900. For the 

 same reason, perhaps, we find no mention of the 

 I'orbes stereoscopic range-finder, or of the Aitchison 

 prism binocular. 



To those interested in the history of optics, and 

 more especially to workers in stereoscopy, von Rohr's 

 compilation will be of great value. For the general 

 render it is to be feared the technical manner in which 

 the subject is presented throughout will prove some- 

 what of a stumbling block. This is, we think, a 

 matter for regret. 



.LU£/?/r.4.V VHYSICAL GEOGRAPHY. 

 Pliysiograpliy. By Prof. R. D. Salisbury. Pp. xx + 770; 

 xxvi plates, 707 figures. (London : J. Murray, 

 1907.) Price 2is. net. 



THE large three-volume text-book of geology by 

 Profs. Chamberlin and Salisbury has gained a 

 firm place in this country owing to its full treatment 

 of many questions, inadequatelv discussed in previous 

 available English text-books. This companion 

 volume on physical geography by Prof. Salisbury will 

 accordingly be welcomed by British teachers of 

 geology and geography. It is of great educational 

 value owing to its wealth of lucid illustration and 

 its clearness of exposition, while it will be indis- 

 pensable as a reference work in geographical 

 libraries owing to its detailed information regarding 

 the physical geography of the United States. 



The book is entitled " Physiography," but the term 

 is used, as the author remarks in his introduction, as 

 a svnonym for physical geography, for it excludes 

 manv subjects which are included in physiography as 

 that science was defined by Huxley and is accepted in 

 the British Isles. The book consists in the main of 

 a description of the structure of the earth's crust, of 

 the working of the various agencies that attack it, 

 and an account of the atmosphere and the oceans in 

 so far as they affect the surface of the earth. Per- 

 haps the most striking feature of the book is its illus- 

 trations, which are very numerous, well selected, and 

 excellently reproduced. They are so clear that the 

 author has been able to abridge his text, leaving his 

 series of photographs to tell their own story. The 

 excellence of the illustrations is probably in part 

 secured bv the use of heavy paper, so that the volume 

 is of such weight as to hamper its use as a student's 

 text-book. 



.As a book of reference its especial value is in its 

 descriptions of the phenomena of physical geography 

 taken from a country where tic illustrations are un- 

 usually clear and suggestive ; and it gives most useful 

 -.ummaries of such well-known geographical incidents 

 a-> the San Francisco earthquake and of the fault 

 which caused it; of the storm which destroyed Gal- 

 NO. 2001, VOL. 77] 



veston in 1900, and the tornado which devastated 

 Louisville in 1896. 



In the chapter on the " weather-maps," the author 

 summarises various reasons for the failure of weather 

 piedictions, and he remarks that occasional mistakes 

 are inevitable, and that one mistake is remembered 

 longer than many correct forecasts. He claims that 

 in many cases the .American forecasts have been of 

 immense economic value ; for example, fifteen million 

 dollars' worth of property were saved in 1897 by warn- ' 

 ings of impending floods; on one occasion half a mil- 

 lion dollars' worth of fruit about Jacksonville, in 

 Florida, and during 1901, 3,400,000 dollars' worth of 

 produce were saved by warnings of approaching cold ; 

 the forecasts also render it possible to avoid unneces- 

 sary risks, as when, in September, 1903, vessels 

 valued at 585,000 dollars were detained in ports on the 

 coast of Florida, and thus avoided a heavy storm. 



In a work of so wide a scope there are naturally 

 many points on which there is room for difference of 

 opinion, but the author is cautious and fair in his 

 treatment of all controverted questions. We are glad 

 to find that he is emphatic in his statement that the 

 term " Gulf Stream " is of doubtful propriety for any- 

 thing beyond Newfoundland, and that the climate of 

 north-western Europe would be much more temperate 

 than that of corresponding latitudes of North America 

 even if there were no Gulf Stream (pp. 544-5). 



He holds that the only explanation of glacial 

 periods which has not been discredited is that based 

 on variations in the composition of the atmosphere. 

 In his discussion of the question there is no criticism 

 of Schloesing's view as to the control of the amount 

 of atmospheric carbonic acid by the sea. The author 

 is a firm adherent of the view of the ice erosion of 

 fiords. 



Each chapter is followed by a table of useful exer- 

 cises, and by a list of references to literature. Thty 

 are mainly from American sources, which is natural 

 in a book designed for American students, 

 but an English edition might have included more 

 references to work easily available to British students; 

 for instance, among the excellent illustrations and 

 account of the eruption of Mt. Pelee and St. Vincent, 

 there is no reference to the reports of Anderson and 

 Flett. It may also be remarked that the Aconcagua 

 ascent no longer holds the record, and that while it 

 did, Zurbriggen was not the only man who had made 

 it- J. W. G. 



POLYPERIODIC FUNCTIONS. 

 An Introduction to the Theory of Multiply-Periodic 

 Functions. By Dr. H. F. Baker. Pp. xvi + 336. 

 (Cambridge : University Press, 1907.) Price 

 I2S. 6d. net. 



THE saying that // n'y a que le premier pas qui 

 coi'ite certainly does not hold good of mathe- 

 matics; and, oddly enough, it conspicuously fails in 

 cases where it might be expected to justify itself. 

 It is but a step from elliptic to hyperelliptic, from 

 single to double Theta-functions ; yet whereas Jacobi 

 reduced all the essential theory of elliptic functions 

 to a most elegant, and for some purposes a final. 



