LEAD ARSENATE. 32 I 



The ditcRes recommended for draining this marsh should be 

 from six to twelve inches wide and about two feet deep. Good 

 drainage should be secured by placing the ditches one hundred 

 feet apart. Without taking any measurements, I should judge 

 that about one thousand feet of ditch would be required to drain 

 the area examined. There are already a f6w ditches which could 

 be cleared and deepened. Probably a good laborer could put 

 the area in a safe condition in about eight or ten days, j 



The mosquito larvae found in these various pools were about 

 full-grown, and to destroy these I would recommend the use of 

 kerosene oil. This can be applied with a watering pot having 

 a fine rose. 



Mr. McCook soon oiled the worst areas, with satisfactory 

 results-, but no draining was attempted. It is usually possible, 

 by the expenditure of moderate sums of money in draining and 

 filling, to do away with the wholesale breeding of mosquitoes. 

 The inhabitants of each neighborhood should cooperate to make 

 the locality as attractive as possible — and one of the first things 

 to be done in each settlement along the Connecticut coast is to 

 abolish the pools of stagnant water where mosquitoes breed. 

 If permanent ditching cannot be started, oiling the pools will 

 afford temporary relief, but in order to be effective it should be 

 repeated once in ten days or two weeks during the mosquito 

 season. 



THE CHEMICAL COMPOSITION OF LEAD ARSEN- 

 ATE AND PARIS GREEN.* 



By John Phillips Street.! 



The constantly increasing use of insecticides in various spray- 

 ing mixtures makes the effectiveness and the cheapness of the 

 poisons used a matter of considerable practical importance. Paris 

 green has been more commonly used for many years than any 

 other arsenical insecticide, and has proved very effective. There 

 is, however, a certain serious objection to its use; the partial 



* This paper, with the directions following it by Mr. Britton, was printed 

 as Bulletin 157 and distributed in September. It is here placed in more 

 permanent form with slight emendations. 



t The analyses of Paris green have been made by Messrs. E. M. Bailey 

 and E. J. Shanley; those of lead arsenate by the writer. 



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