76 



may be more than is required at ordinary times, but occasions may 

 arise when more power would l)e desired. 



There are many methods by which gasoline is fed into the cylinders 

 of these engines. The better engines have a pump by which the gas- 

 oline is forced into the cylinder. The ignition is accomplished by one 

 of two methods — either by an ignition burner on the outside of the 

 cylinder which communicates heat to a platinum point which explodes 

 the gasoline vapor, or by an electric spark from an induction coil 

 which is connected with numerous dry batteries. The cooling tank 

 used with these engines for the purpose of keeping the cylinder moist 

 and cool is usually from 12 to 14 inches in diameter. This size is 

 intended for stationary engines, where the water can not be renewed 

 frequently. In spraying, however, the water can be renewed ever}^ 

 few hours if necessary; and therefore the tanks can be built as small 

 as 6 inches in diameter, which will make a considerable reduction in 

 the weight of the machinery. 



Purchasers are always given full instructions in regard to the care 

 and running of these engines, so that one with comparativeh' little 

 mechanical ingenuity has very little trouble. The greatest source of 

 difficulty is with the electric current. The insulations often become 

 imperfect or the sparking points become dirty and fail to produce a 

 spark. By carefully testing the current and keeping these points 

 clean practically all of the trouble is avoided. 



It is preferable to place the engine at the rear end of the frame and 

 the pump as near the engine as possible. There are two tj'pes of spra}'- 

 ing pumps which ma}" be used for this purpose — the triplex pump, 

 which consists of three vertical plungers, and the straight horizontal 

 double-acting force pump. Either of these pumps will be found to 

 answer to the conditions required for these outfits, but the horizontal 

 pump is more commonly used. The pumps should be so manufactured 

 that all of the parts are accessible and the brass lining easily removed. 

 The working parts should be made of brass or bronze. A large air 

 chamber is essential, as well as a pressure gauge. It is absolutely 

 necessary that a relief valve be attached to the pump, so that when 

 the stopcocks on the bamboo extension are closed the engine will not 

 have to be stopped, but at a certain pressure the spraying liquid will 

 be returned to the tank. 



In sections of the country where irrigation is practiced it has been 

 found that the most effective method of filling the tank is to have 

 another pump which can be attached to the engine, by which water 

 can be pumped from an irrigating ditch into the tank. This pump 

 should belong to the type known as "low-down pumps," which 

 deliver large quantities of water at low pressure. The suction hose 

 should be 2 or 3 inches in diameter and the end which is put into the 

 irrigating ditch should be w T screened. There is usually some 



