March 5, rqo^] 



NATURE 



411 



other than lead, and though the attempts to find some 

 satisfactory substitute for the lead cell have been many, 

 the results have been in all cases disappointing ; it re- 

 mains to be seen whether Mr. Edison's iron / nickel- 

 oxide combination will prove any more practical than 

 its forerunners. As yet the trustworthy information con- 

 cerning its behaviour and durability is too meagre for 

 any prophecy as to its future to be made. 



We have left the contents of chapters iv. and v. to 

 the last, as these contain what to many will doubtless 

 prove the most interesting part of the book. In chapter 

 iv. , on the properties and behaviour of lead cells, the 

 electrical phenomena which a complete theory of the 

 chemical reactions must explain are described, and in 

 chapter v. the author deals with the theories which have 

 been advanced. The information as to the electrical 

 behaviour is full and comprehensive, and typical curves 

 of charge and discharge under various conditions are 

 given. These points have been very thoroughly studied 

 both in commercial and in experimental cells, and it 

 is perhaps surprising that their theoretical explanation 

 has proved so difficult. Mr. Wade's views were ex- 

 pressed in his paper read before the Institution of Elec- 

 trical Engineers three years ago, and they are here re- 

 peated. The cycle of changes taking place on discharge, 

 reversal and recharge is explained as being due to 

 changes in a complex lead molecule on the one hand, 

 and a similarly complex lead-peroxide molecule on the 

 other. Double sulphation results from the addition of 

 (SO,) groups one by one (with corresponding removal 

 of 2 on the peroxide plate), but the process does not 

 go on until the active material has the composition 

 Pb 12 (S0 4 ) 12 (on the assumption of initial composition 

 Pb 12 and Pb 12 24 respectively) on both plates. When 

 the active materials have the compositions Pb,,(S0 4 ) 8 

 and Pb,„0 6 (S0 4 ) g the plates are fully discharged. If 

 the current be now kept flowing in the same direction 

 reversal sets in with addition of O, at the negative, 

 and its removal at the positive, and this goes on until 

 Pb 12 O s (S0 4 ) s and Pb I2 (S0 4 ) s are formed; continuing 

 the current still in the same direction 2 is added and 

 (SO,) removed at the (old) negative and (S0 4 ) removed 

 at the (old) positive, until finally Pb 12 21 and Pb 12 are 

 reformed, and the cell is fully charged, but with the 

 plates reversed. 



This explanation, it is true, helps to explain some 

 of the obscure points in the behaviour of lead and 

 lead peroxide in the accumulator, but it is question- 

 able whether the weight of evidence in its favour is 

 sufficient to justify the assumptions necessary, even 

 though these may be to some extent supported by 

 collateral evidence of a purely chemical nature. The 

 truth of the matter seems to be that at present we can- 

 not go much beyond the double sulphation theory 

 originally put forward in these columns by Gladstone 

 and Tribe. Progress is barred, not so much by want of 

 study of the lead cell as by want of knowledge of the 

 general behaviour of lead compounds during electro- 

 lysis, and even by ignorance of the reactions occurring 

 on the electrolysis of sulphuric acid. In these cir- 

 cumstances, we can look for little help from the dis- 

 sociation theory, nor has it, as Mr. Wade remarks, 



NO. 1740, VOL. 67] 



thrown any light on the problems presented, and 

 thermochemical calculations cannot be of great assist- 

 ance either. 



We have dealt with Mr. Wade's book at some 

 length, but not at a greater length than its merits 

 deserve. It only remains to give a word of praise to 

 the illustrations, which, especially in the case of the 

 pictures of different grids and supports, are very clearly 

 executed, and considerably enhance the value of the 

 book. Maurice Solomon. 



BIOLOGY OF THE LAKE OF GENEVA. 

 LeLiman. Monographie limnologique. Tome troisieme, 

 premiere livraison. Par Prof. F. A. Forel. Pp. 411. 

 (Lausanne : F. Rouge, 1902.) 



IN this, the first portion of the third volume of his 

 interesting work, Prof. Forel treats of the biology of 

 the Lake of Geneva, and describes with his customary 

 wealth of detail the various forms of life observed in and 

 upon the waters of the lake. From a biological point of 

 view, Prof. Forel divides the lake into three regions : 

 (a) littoral^ extending from the shore line down to a 

 depth of fifteen metres ; (b) abyssal {profonde), com- 

 prising a layer of water about two metres in depth 

 extending from the littoral region all over the bottom of 

 the lake ; (c) pelagic, the great mass of water beyond the 

 littoral region and above the abyssal region. The fauna 

 and flora are classified in accordance with these three 

 regions, and as the animals and plants exist in intimate 

 biological relation, they form what Prof. Forel describes 

 as " societes," so that there is a "societe" pertaining to 

 each region. Descriptions and illustrations are given of 

 the methods and apparatus employed in collecting the 

 organisms in the different regions, and in the sorting out 

 and separation of these organisms when obtained. 



The first half of the book is occupied chiefly with a 

 full list of the organisms constituting the fauna and flora 

 of the lake. Prof. Forel enumerates in all nearly one 

 thousand species. Many of these, however, such as the 

 bats and some of the birds, have no claim to be con- 

 sidered natives, but, like Homo sapiens, who heads the 

 list, resort to the lake in search of a living. On the 

 other hand, there are many species peculiar to the lake, 

 among which the most interesting are those adapted to 

 live at considerable depths. The most remarkable of 

 these abyssal forms are the blind Crustacea, Asellus 

 Foreli and Niphargus Foreli, but most of the groups of 

 animals occurring in the lake have representatives in the 

 deep fauna. Among plants, the only peculiar abyssal 

 form is a moss, Thamnium Lemani, found at a depth of 

 nearly 200 feet, yet brilliantly green. 



In some groups, the lake is very rich in species, while 

 in others it is surprisingly poor. This may be partly due 

 to some groups having been more thoroughly studied 

 than others. 



Of the seven species of mammals noted, one, the 

 beaver, is extinct, two, on Prof. Forel's own showing, 

 have not yet been recorded with certainty, while three 

 are classed as " erratic " or adventitious, leaving only the 

 otter as a regular inhabitant. There is a long list of 



