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POPULAR SCIENCE MONTHLY. 



Hill laboratory and constant use resulted in important improvements. 

 The old method of obtaining the temperature of water beneath the sur- 

 face by the use of a weighted thermometer gave way to the electrical 

 'thermophone/ and new methods for measuring the color of water were 

 devised. An apparatus for photography was installed, and excellent 

 photographs were made of all the important microscopic organisms in 

 the water. A set of these photographs was on exhibition at the World's 

 Fair in Chicago. In addition to the routine work, many lines of experi- 

 mental work were undertaken. Studies were made upon the seasonal 

 distribution of various organisms, the effect of temperature, light and air 

 upon their growth, and upon the cause and nature of the odor imparted 

 by organisms to drinking water. The effect of swamp-land upon water 



Fig. 1. Mt. Prospect Laboratory, Brooklyn, N. Y. 



supplies, the stagnation of deep lakes, the bleaching action of sunlight 

 upon colored waters were likewise considered, while for several years the 

 laboratory was operated in connection with an experimental filter plant. 

 After the Metropolitan Water Board assumed control of the water 

 supply of Boston and its suburbs the laboratory was moved from Chest- 

 nut Hill Reservoir into the city, where it now occupies rooms at No. 3 

 Mt. Vernon street. In 1897 Dr. F. S. Hollis succeeded the writer as 

 biologist, and he in turn lias been succeeded by Mr. Horatio N. Parker. 

 During recent years the conditions of the water supply have changed. 

 New reservoirs of large capacity have been built, and the great Wachu- 

 sett Reservoir is in process of construction. Swamps have been drained 

 and fillers have been installed where there was danger of polluted water 



