March 3, 1898J 



NATURE 



411 



Similarly, in the case of the Bunsen cell the student is | 

 informed that, "the H^, appearing simultaneously at 

 the carbon pole(?) is oxidised into H.,0 by the nitric 

 acid." It is surely a new discovery that hydrogen 

 appears at the negative plate in these elements, and 

 one well calculated to upset all present electrolytic 

 hypotheses. 



The induction coil and its action are next considered, 

 and here again some mistakes occur. 



"The E.M.F. of the induced current depends upon 

 several factors : (i) It is directly proportional to the 

 intensity of the current change in the first wire. (2) It 

 is directly proportional to the rate of change of the 

 inducing current." 



It is difficult to see any difference between (i) and (2) ; 

 there is probably a misprint somewhere, but this is 

 precisely the kind of blunder most calculated to waste 

 the time and temper of a student who is not strong in 

 physics. In describing the theory of the extra currents 

 of make and break it is stated that — 



"as the duration of this induced current (the extra 

 current at make) is very short its effect is soon ex- 

 hausted, but not before it has produced the result that 

 more time is required for the current to reach its full 

 strength than would have been the case if the wire had 

 been perfectly straight." 



Now the extra current at make lasts just as long as 

 there is any variation of the primary current, and there- 

 fore as long as there is any induced current in the 

 secondary coil, and its effect is no sooner over than any 

 of the other effects involved. 



A further error in connection with the same subject is 

 worth noting, since it is not peculiar to this volume, but 

 occurs in other text-books of physiology. 



"On breaking the circuit the circuit of the primary is 

 broken, so that no induction currents can be set up in 

 the primary." 



" The fall in potential is therefore instantaneous." 



Now the fall in potential at break is not instantaneous, 

 otherwise the E.M.F. of the induced current in the 

 secondar)' circuit would be infinitely great. The primary 

 circuit cannot by any means be instantly broken, and 

 there is an induced extra current in the primary at 

 break. Only in the circuit during break there is a high 

 resistance in the spark gap, and both the extra current 

 and the primary current are rapidly diminished by this 

 rapidly increasing resistance. 



The more purely physiological part of the book is 

 fairly well written, and contains descriptions and figures 

 of new and sometimes ingenious adaptations of simple 

 apparatus for experimental work. Some of these artifices 

 for making simple apparatus are certain to become 

 extensively used, and it is here that the book will 

 probably render most assistance to teachers of physi- 

 ology. The book is also copiously illustrated, and contains 

 a large number of reproductions of experimental tracings. 

 Many of these it is impossible for the student to imitate 

 for himself, but they will doubtless form valuable aids 

 in assisting him to recollect the results of class 

 demonstrations. 



NO, 1479, VOL. 57] 



OUR BOOK SHELF. 



L. Riitivieyer. Gesavimelte Kleine Schriften allgemeinen 

 Inhalts aus dem Gebiete der Naiumnssenschaft. Nebst 

 einer atiiobiographischen Skizze. Edited by H. G, 

 Stehlin. 2 vols. 8vo. Pp. iv + 400 and 455. With 

 a portrait and woodcuts. (Basel : Georg et C'% 

 1898.) 



In these two well-printed and handy volumes we have 

 the more important of the contributions made to science 

 by the late Prof Riitimeyer, which could be reproduced 

 without costly illustrations. By the kindly care of 

 Leopold Riitimeyer and H. G. Stehlin, we have these 

 as an " In Memoriam " tribute, the crowning stone of 

 which is the very interesting series of notes by Prof. 

 Riitimeyer himself of the chief incidents of his life. In 

 a work of this nature, there is left but little room for 

 criticism, and we will serve the reader's purpose best 

 by a brief notice of the contents of the volumes. In the 

 stray memories of his scientific life we learn that, born 

 in February 1825, his early days were spent in the 

 country ; his life was in the open air, wandering over 

 field and meadow, in woods, and up the hill-tops. Edu- 

 cated at home, he records his happiness at having 

 escaped the mischiefs and sorrows of a public school. 

 When sixteen years old, falling under the influence of 

 Bernhardt Studer, his studies took the direction of the 

 natural sciences, and his future career was marked out. 

 In these " Memories" many are the interesting facts re- 

 corded in a busy life. As an author he began with a 

 " Memoir on the Nummulitic Region of the Bernese 

 Alps," which was published in 1848, and we have on 

 record a long list, published from year to year, with but 

 few exceptions, until 1895, when in June he put his initials 

 to the " Memories," passing out of the world, though not 

 beyond memory, on the 25th of the following November. 

 Ever fond of nature, his latter years were rendered 

 happier by winter sojourns in the sunny south of Europe. 



The memoirs in the first volume are chiefly of a 

 zoological character. We find an essay on the form and 

 history of the vertebrate skeleton ; on the historic method 

 in palaeontology ; on the origin of our animal kingdom ; 

 on the limits of the animal kingdom— a critical notice on 

 Darwin's writings ; on the alterations in the animal life 

 in Switzerland, since the appearance of man ; on the 

 evolution of organic beings. Most of these memoirs 

 were at one time of interest, but while they were, as we 

 think, worth gathering into a volume, it must be con- 

 fessed that the greater part of their novelty has gone. 



The second volume contains a long essay, " Vom Meer 

 bis nach den .\lpen," being a sketch of the structure, form 

 and colour of the country met with in a section between 

 England and Sicily ; also a paper on the people of the 

 Alps ; a glance at the history of glacier studies in 

 Switzerland ; a very brightly written sketch of Brittany 

 and its people. Obituary notices of Louis Agassiz, 

 Charles Darwin, Peter Merian, and Bernhardt Studer, 

 bring this volume to an end. There is in an appendix a 

 list of all Riitimeyei-'s writings, arranged in chronological 

 order. 



Recherches experimentales stir quelques Actinomitres 

 ilectro-chiiniques. By H. Rigollot, Docteur ^s Sciences, 

 Chef des travaux de Physique a I'Universite de Lyon. 

 Pp. vi -f- 138. (Paris : Masson et C*% 1897.) 



In this work M. 'Rigollot has collected together, in a 

 convenient form, his researches on photo-electric cells. 

 Two metallic plates being immersed in an electrolyte, 

 and the one exposed to light whilst the other is protected 

 from it, a difference of potential is established between 

 them. The author gives the large amount of valuable 

 information, which he has accumulated in his study of 

 this phenomenon, in the form of experimental results ; 



