75 
consists of five to ten thousand trees, it will be found that the ex|K'nso 
per tree with this outfit is only about half of what it would b<' with 
hand-power sprayers. 
Many dealers have placed spraying machines on the market in which 
the power is derived from gasoline engines. They consist largely of 
engines, pumps, and machinery for other uses, placed together for 
this purpose. AVhile a majority of these are quite well adapted to 
the work of spraying, many improvements are possible which would 
Fig. 17 —Spraying outfit for treating tall trees (after Gould). 
increase ethciency without inricasing rost. There are many makes of 
gasoline engines, most of which are well adaptod to this work. The 
horsepower of the engines is usually too large. An outfit with which 
the writer is most familiar is run ))y a 1 V-horsepower gasoline engine, 
and in ordinary spraying optMations it was found that the engine was 
too powerful, as four out of nine possible explosions were all that was 
recjuired to run th(^ ])unips and k(M'))tht> pressure at l(M) pounds. The 
engiiK^ for spraying purposes should Uo about 1 horst^pi>W('r. which 
