ALGAE IN WATER SUPPLIES 95 



to one million, which in all cases would be sufficient to prevent the growth of a polluting 

 algal form, it would be necessary to drink something over twenty quarts of water a day 

 before an amount which is universally recognized as harmless would be introduced into the 

 system, while more than fifty quarts would have to be consumed before there would be 

 danger of producing an unpleasant or undesirable effect. As will be seen from the pre- 

 ceding tables the use of copper sulphate at this maximum strength of one to one million 

 would need to be resorted to only in extreme cases, and for a very short length of time, 

 for, the reservoir once entirely free from the organisms, a very much weaker solution would 

 be sufficient should any further application be necessary. 



The Report of the Massachusetts State Board of Health for 1905 stated 

 as follows : 



The objectionable tastes and odors of pond and reservoir waters, which are often at- 

 tributed to decaying fish and other causes, are, in practically all cases which have been 

 brought to the attention of the Board, caused by the presence of organisms, in some cases 

 of kinds which attach themselves to the sides and bottom of the reservoir, but in the 

 majority of cases of those kinds which live in suspension in the water. Early in 1903, Dr. 

 George T. Moore formerly Algologist of the United States Department of Agriculture, 

 brought to the attention of the Board the results of investigations which he had made, 

 indicating that the microscopic organisms which are the chief cause of objectionable tastes 

 and odors in the waters of ponds and reservoirs could be destroyed by applying sulphate 

 of copper or blue vitrol to the water in very small quantities; and information was also 

 submitted tending to show that bacteria were also destroyed in water brought in contact 

 with metallic copper. 



The results of some of the experiments and investigations so far as obtained tend to 

 support the conclusions which had been reached when the matter was first brought to the 

 attention of the Board as to the practicability of the copper treatment for the removal of 

 growths of organisms and bacteria, but the results of other experiments conflict with some 

 of these conclusions. Further study and experiment are necessary before the probable results 

 of the use of copper in preventing objectionable conditions resulting from growths of or- 

 ganisms, or the probable effect of the use of this substance in public water supplies upon 

 the public health can be conclusively determined. 

 Dr. Moore states that : 



Spirogyra is often the cause of considerable trouble in a mechanical way, and on account 

 of its method of forming resting spores is usually able to withstand the most unfavorable 

 conditions to which it may be subjected in a pond or reservoir. In at least one instance this 

 alga has been the cause of the loss of thousands of dollars by the damage it produced in 

 smothering out the young water-cress plants in the artificial beds constructed for the winter 

 propagation of this vegetable. When the cress is cut for market, it necessarily leaves the 

 plants in a weakened condition, and if the Spirogyra gets a start it will form a thick, 

 heavy mat over the water, which is sufficient to prevent the growth, if not entirely to kill, 

 the cress plants. 



