SPRAYIXG APPAEATUS. 147 



Thorough and constant stirring is the prime requisite for 

 obtaining satisfactory and uniform results in spraying, as 

 the arsenical compounds used do not enter into true solution 

 with water, but having greater specific gravity remain in sus- 

 pension only. For this reason the particles of the poison 

 have a constant tendency to settle to the bottom of the tank. 

 Therefore the strength of the solution varies accordino; to 

 the amount of agitation given it. Hence the necessity of 

 a continuous stirring of the contents of the spraying tank 

 even when the pump is not being used, as while it is 

 beino; taken from one tree to another. Even with con- 

 tinuous stirring the liquid issuing from the nozzle when 

 the tank was nearly emptied usually contained more poison 

 than that taken from a full tank or one half full. In most 

 spraying machines the liquid is agitated only when the pump 

 is in motion and the insecticide settles when the pump is 

 not in use. It then becomes necessary to scrape the bottom 

 of the tank and stir vigorously. 



Several kinds of hose were used in spraying. The half- 

 inch, rubber-lined, cotton-covered Eureka hose was found to 

 be most convenient for the heavy apparatus on account of 

 its light weight. For light machines, where only one small 

 nozzle is used to each line of hose, quarter-inch rubber tub- 

 ing is large enough. Each spraying gang was supplied with 

 eight pieces of hose, each fifty feet in length, which were 

 used in two lines of two hundred feet each. These were 

 sometimes united to form a single line so as to spray places 

 which, from their locality, could not be reached otherwise. 

 In general use, however, the two lines of hose were used 

 simultaneously. A " shut ofi"" was coupled on each line of 

 hose near the pump and also at the nozzle. 



Not the least important part of the spraying apparatus is 

 the nozzle. The desirable qualities of a nozzle for spraying 

 large trees are that it shall throw voluminous jets of spray 

 to a distance of eight or ten feet, clear itself readily, and 

 be easily adjusted to varying distances, thus enabling the 

 workmen to work rapidly. A series of tests was made with 

 thirty-three difierent kinds of nozzles. The Lowell and Gem 

 nozzles were found to be most effective. Both of these noz- 



