and Laboratory Methods. 1553 



Whipple, Geo. C. Changes that Take Place in The author has undertaken a study of 

 the Bacterial Contents of Waters during ^, j.^. , i_- i ^i i 



Transportation. Tech. Quart. 14 : 21, 1900 the conditions under which the number 



of bacteria in samples of water for 

 analysis increase or decrease during transportation from the point of collection 

 to the laboratory, a subject of considerable interest to those engaged in bacteri- 

 ological analysis of drinking waters. He reaches two conclusions : 1. After a 

 sample of water is collected, either in large or small bottles, there is, first, a 

 slight reduction in the number of bacteria, due to the change in environment. 

 The reduction is greater when small volumes of water are collected. Subse- 

 quently, there is an increase in the number of bacteria, which is greater in a 

 small bottle than in a large one, and is more rapid when the bottle is but par- 

 tially filled. With bottles of the same size the growth is more rapid in small vol- 

 umes of water than in large volumes. 2. An agitation of the water exercises 

 a slight retarding influence upon the multiplication of bacteria, but the shaking 

 to which the water samples are liable during transportation is so slight, that it is 

 of practically no importance in affecting the number of bacteria in the water. 



H. w. c. 



NOTES ON RECENT MINERALOGICAL 

 LITERATURE. 



Alfred J. Moses and Lea McI. Luquer. 



Books and reprints for review should be sent to AKred J. Moses, Columbia University, 



New York. N. Y. 



Vernadsky W. Zur Theorie der Silicate. ^ theoretical discussion limited to the 

 Zeit. f. Kryst, 34: 37-66, 1901. 



simpler and better known compounds. 



All historical and bibliographic data are omitted, though included in a previous 



article in a Russian journal. 



Natural silicates are usually isomorphic mixtures, that is, are analagous to 

 solid solutions, some predominating substance (the " solvent ") containing dis- 

 solved in it other substances, necessarily crystallizing i?i the same one of the thirty- 

 two classes, but possibly of very different type of formula. 



If the "solvent" contain no R2O3 we may call the silicate a simple 

 (einfache) silicate. 



If the "solvent" contain R2O3 the silicate may be called an alumosilicate, 

 ferrisilicate, borosilicate, etc. Only the alumosilicates are directly discussed, the 

 others may be considered by analogy. 



There is a sharp line between simple and alumosilicates : 



{a) There is no known reaction by which the metals of RO can be replaced 

 by Al, or conversely. 



if) There is no known reaction by which the alumosilicates can be directly 

 changed into silica hydrate, (opal) or conversely. 



(<:) The alteration products of simple silicates often include opal and quartz ; 

 the alumosilicates can only with very uncommon proportions yield opal (and 

 aluminum hydrate), but usually yield only clay and minerals of the chlorite group. 



