WATER SUPPLY 81 



The first section of tlio ('.\liil)it deals with the luitunil liistory of wjitcr 

 supply us it allects the life and liealth ol' man. Large photo- 

 Water Supply graphs at the entrance to the corridor on the left illustrate 

 the primary source of water supply, the clouds, and the 

 secondary sources, the rivers and lak(>s. Diagrams, models and a relief 

 map show the variations in rainfall at different points in the United States. 

 Relief maps of the region about Clinton, Massachusetts, before and after 

 the construction of the Wachusett Reservoir for tlie water-supply of Boston, 

 show the way in which surface water supplies are collected by impounding 

 streams, and a model of a well sunk through impervious to water-bearing 

 strata shows how ground-water supplies are obtained. A series of samples 

 and models illustrate the variations in composition which occur in natural 

 waters, from the swamps of Virginia to the deep wells of Iowa and the 

 turbid rivers of the Ohio valley. 



Some of the principal micro-organisms, Algse and Protozoa, which 

 grow in reservoirs and impart tastes and odors to water are represented 

 by a series of glass models. The effect produced by the pollution of water 

 by disease germs is illustrated by relief maps and diagrams showing the 

 course of famous typhoid and cholera epidemics. Models are displayed 

 which illustrate the purification of w^ater by storage, filtration and disin- 

 fection, the filter model being an elaborate representation of the plant at 

 Little Falls, N. J. Diagrams and models indicate the results of water 

 purification as measured both in dollars and cents and in the saving of 

 human life. Finally a series of five large relief maps shows the growth 

 and development of the water supply of New York City. 



Following the water-supply exliibit is a series of models illustrating 

 the dangers from improper disposal of the liquid wastes 



p.. Wastes ^^ ^^^ ^^^^ ^^^ ^^^ ^^^^ ^^^ ^^ avoided. Actual points 

 of danger in the neighborhood of New York are shown 

 where polluted harbor w^aters, bathing places and shell-fish beds are a 

 menace to health. The modern methods for the treatment of sewage on 

 scientific lines are illustrated by a series of models of screens, sedimenta- 

 tion tanks and filter beds of various types. 



The cases near the window are devoted to the group of Bacteria, espe- 



-, ^ . cially in their relation to human life. Glass models show the 



Bacteria • i i , 



various shapes and relative sizes of these minute forms and 



in particular of the principal types w^hich cause disease. In a nearby case 

 are displaj-ed actual colonies of a number of species of bacteria including 

 some w^hich produce disease and others w^hich are beneficial to man by their 

 effect upon soil fertility or the fact that they may be utilized in the pro- 

 duction of substances useful as foods or in the arts. A group of trans- 

 parencies at the window show^s some of the more important disease bacteria 

 as they appear under the microscope. 



