April 28, 1905.] 



SCIENCE. 



653 



tion may be called to those discrepancies 

 by a coadjutor more recently fi'om the 

 schools, nevertheless the breadth of his ex- 

 perience assures the more mature man that 

 his judgment is not at fault and it is ex- 

 perience that is of value in the end. 



In conclusion, a word may be pardoned 

 concerning a matter which has received 

 more or less attention of late from the 

 public press, namely, the treatment of 

 reservoir water with copper sulphate for 

 the purpose of destroying suspended or- 

 ganisms. No doubt whatever exists that 

 a sufficiency of the salt will destroy aquatic 

 life, and the amount required to dispose of 

 such as produce objectionable taste and 

 smell is certainly very small. 



What the public are anxious about, how- 

 ever, is whether or not the salts of copper 

 are to be classed with those of lead as 

 cumulative poisons. Unfortunately, the 

 answer to that question is not very satis- 

 factory at the present moment. We do 

 not possess as much light upon the point 

 as we should wish. 



Copper is eliminated by the liver and 

 kidneys, and some hold that there is a tend- 

 ency towards an accumulation of the metal 

 in the liver, and that 'elimination is only 

 complete when eliminating organs are 

 sound. ' This appears reasonable. On the 

 other hand, we should be reminded that the 

 use of copper sulphate for preventing algal 

 growth is but occasional, and that no neces- 

 sity is at hand for asking the people to 

 constantly use a water treated with the 

 salt. 



A dose of the chemical is administered 

 to the reservoir water; the objectionable 

 plants are killed thereby and no further 

 dosing is required during a considerable 

 interval of time. Let it be noted, there- 

 fore, that the amount of copper used is 

 minute, that all of it does not remain in 

 solution, and that its use is not continuous. 



As to the employment of copper sulphate 



for the killing of pathogenic bacteria the 

 case is quite different. Under such condi- 

 tions the amount of the sulphate required 

 has to be greatly inerea,sed, and, what is 

 still more objectionable, its addition to the 

 water supply must be constant, because of 

 the continual presence of the organisms 

 which require removal. It may well be 

 urged that the use of a 'disinfected' water 

 supply would be opposed by the average 

 citizen upon pretty much the same ground 

 that he would object to the use of em- 

 balmed beef. 



Some modification of the copper process 

 for the killing of disease germs may yet be 

 suggested which will excite the prejudice 

 in the popular mind against 'chemicals' to 

 no greater degree than does the employ- 

 ment of alum in mechanical filtration, but 

 that day is scarcely here as yet. Let it not 

 be forgotten, however, that its use for re- 

 moval of those algal growths which have 

 given us so much trouble in the past is to 

 be encouraged, and that the authors of the 

 process are deserving of much praise for 

 their contribution to the growing field of 

 'water supply.' 



W. P. Mason. 



SCIENTIFIC BOOKS. 

 A NEW INTRODUCTION TO THE STUDY OF FISHES. 



1. 



A FULL fourth of a century had passed since 

 the publication of a general work in English* 

 on systematic ichthyology before a new one 

 appeared to take its place. It was in 1880 

 that ' An Introduction to the Study of Fishes 

 by Albert C. L. G. Giinther ' appeared. That 

 work, however, by no means represented the 

 condition of science at the time of its issue, 

 and was replete with errors as well as 

 anachronisms of all kinds. Its author was 



* E. Perrier's corresponding portions of his 

 French work (Traits de Zoologie) were mostly 

 published less than a year before (1903), and, if 

 put in the same typographical dress, would cover 

 nearly two fifths more space. 



