124 Roosevelt Wild Life Bulletin 



connection with the construction of the Ashokan and Kensico reser- 

 voir of the New York City water supply, the essential parts of 

 which have been reprinted by Whipple ('14). They discuss the 

 cases where all the soil has been stripped from prospective sites oC 

 reservoirs, and show that the removal of the earth reduces con- 

 siderably the growth of algae but is not a sure preventive. In the 

 case of the Park lakes constructed for pleasure purposes only, even 

 more than in the case of reservoirs for municipal water supplies, 

 the cost of this soil stripping is prohibitive. The object in soil- 

 stripping is to eliminate a source of decaying organic matter that 

 will furnish material for the growth of algae. This comes in part 

 from the decay of vegetable matter, and conditions in a lake bed 

 may be appreciably bettered by removing all plant growth. They 

 recommended the clearing off and grubbing out of all trees in the 

 proposed site and afterwards a burning off of all the vegetation. 

 In the case of the lakes of the Park this careful removal of the vege- 

 tation is necessary for the utilization of the lakes by campers, since 

 submerged stumps are a constant menace to those using the lakes. 



The point at which the dam is to be built should also be taken into 

 consideration. Too often the engineer, with his mind set solely 

 on construction of a lake at a moderate cost, is tempted to select a 

 flat swampy area since he can then make a large lake cheaply. In 

 these swampy areas, however, there is a large amount of decaying 

 vegetable matter and an enormous potential source of organic matter 

 to supply food materials for the algae for many years to come. It 

 is far better to choose a site where there are no swampy areas, and 

 where the flooding of the lake bed will not produce one with swampy 

 margins. If lakes are placed in valleys fairly free from low wel 

 areas, made reasonably deep, and the beds are suitably cleared before 

 flooding, there should be no excessive growth of algae. 



Removal of Algae by Means of Chemicals. The discussion 

 given above has adduced sufficient evidence, in my opinion, to war- 

 rant the conclusion that the artificial lakes or artificially enlarged 

 natural lakes of the Park will eventually arrive at a state of biological 

 stability where the plankton Myxophyceae will not grow in suffi- 

 cient quantities to affect the use of the lakes as camp sites. Until 

 these lakes develop the normal lacustrine habit of the region, how- 

 ever, disagreeable " blooms" are apt to occur and chemical means 

 for their control should be used. 



The development of algae in natural or artificial bodies of water 

 used for municipal water supplies is of even greater importance 

 because the presence of certain algae may affect the taste even when 

 it does not affect the esthetic or recreational use of a lake. Methods 

 for the control of algal growths have been developed primarily 

 because of this fact. The current practice for the removal of algae 

 rests upon the use of copper sulphate as introduced by Moore and 

 Kellerman C04, '05). At the time of the pubHcation of Moore and 

 Kellerman's method for eradicating algae a great deal of interest 

 was expressed by sanitarians ; and numerous reports of experience 

 with the method are found in the periodical literature ; but with the 



