60 



The Microscope. 



how to do it, it is also possible to get a Rotifer in so small a 

 drop of water that it is? unable to swim out of the field of a 

 quarter-inch objective. I have had it in constant use for ani- 

 mals of all sizes, from the smallest infusoria to tadpoles, and I 

 hope it will be found equally useful to ra}^ fellow pond hunters. 



C. ROUSSELET. 



NCV/ 

 PVBLICATIONS 



An elementary handbook on potable water, by Floyd 

 Davis, Ph. D. 12mo., pp. 118. Boston : Silver, Burdett & Co. 

 Price, $1.00. Prof. Davis is evidently an expert in the chemical 

 and hygienic portions of the subject he has selected for popular 

 treatment in this excellent little book, but on certain points he 

 as evidently feels his incompetency and touches them lightl}^, 

 yet he fails to escape some incorrect statements and some bad 

 teaching. While these blunders mar the fair surface of the com- 

 mendable little work, they should have been eliminated, since 

 the book will be accepted as authoritative, these little errors and 

 all. The chapters treat of pure water, inorganic constituents, 

 vegetable constituents, micro-organisms, water supplies, natural 

 purification, artificial purification, systems for central filtration, 

 with an interesting appendix. The section on central filtration 

 should be read by every board of water commissioners in the 

 country, for it is at the filters that the majority of our water 

 supplies may be vastly improved. 



But while Prof. Davis' book will be acceptable to ever}^ intel- 

 ligent reader, and a source of valuable information to the major- 

 ity of laymen, it contains some statements whicli are not only 

 erroneous, but laughable. Speaking of the animal constituents 

 of water he says (page 34;: ^''Leeches, in this connection, are 

 mere curiosities, still they are sometimes accidentally swallowed 

 in potable water. They are liable to attach themselves on the 

 pharynx, and when once fixed they seldom fall off" spontaneousl3\ 

 Coughing, nausea and spitting of blood are produced b}- them, 



