256 THE AMERICAN MONTHLY [Aug. 



logical point of view." Perhaps it is not too much to hope that 

 such men as Rafter will yet find out just what animals and 

 plants may be used to purify sewage laden streams and how 

 to rear such animals and plants in enormous numbers. 



Among the hopeful animals is Paramecium aurelia, an animal 

 about 1-90 inch in length. It is a filth infusorian, but an in- 

 teresting form for study. Twenty to fifty may o'^ten be found 

 in a single c.c. of contaminated water. A bright green colored 

 infusorian, Euglena viridis, only 1-500 inch in length is oft^n 

 found in standing water. As it multiplies by fission and not 

 sexually, enormous numbers can be produced in a short time. 

 Hydra and the rotifers are also found in bad water. The pre- 

 cise function of each organism is yet to be worked out, though 

 we believe in a general way that they purify the water. 



Entomostraca eat dead animal matter, can be kept alive for 

 months on human excreta and will soon die without it. They 

 in turn constitute an important food for fishes. Those Fish 

 commissioners who are blind to these facts, and most of them 

 are so, are neglecting perhaps the most important topic within 

 their reach. Nature undoubtedly has the requisite agencies for 

 performing economically all these transformations from the 

 worst of filth to healthy organisms. We must wrest from her 

 the secrets of this work. 



The diatoms come in for notice also. In one specimen of 

 water, Rafter found 1792 Synedra. Is their mission healthful? 

 Of Alga% 2664 zoospores were found in one specimen. 



The value of sewage as a fertilizer is declared to be too small 

 for commercial consideration on account of the very great dilu- 

 tion. Comparison is made with a pint of brandy mixed with 

 a hogshead of vvater, or the minute particles of gold contained 

 in the earth npon which Philadelphia is built. In the aggre- 

 gate there is said to be a thousand million dollars worth of gold 

 in the bed of clay in question, but the cost of extracting it 

 would far exceed the j^roduct. 



It is impossible to give an idea of the immense storehouse of 

 knowledge contained in this volume every page of which is 

 strewn with facts bearing upon the problem. The maps, and 

 other illustrations have been prepared at great expense. The 

 price of the book is high, but city and town authorities must 

 have it in the study of sewage disposal. 



