Hill laboratory and constant use resulted in important improvements. The old method of obtaining the temperature of water beneath the surface 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 experimental 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
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 Chestnut 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 has 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 Wachusett Reservoir is in process of construction. Swamps have been drained and fillers have been installed where there was danger of polluted water
