104 



in all cases have all working parts constructed of brass, 

 and really had best be made entirely of brass, when it will 

 last a long time. The barrel is to be fastened upon a 

 wagon, or some vehicle convenient to draw about. Then 

 with plenty of hose and a nozzle discharging a fine spray, 

 the work may be performed quickly and thoroughly. What 

 is desired is to apply a very fine spray to every part of 

 plant or tree, and then stop. A properly sprayed tree will 

 not drip much. Many pumps are provided with so-called 

 agitators to keep the liquid well shaken up and prevent 

 settling, but these must not be depended upon altogether. 

 Frequent hand stirring with a good paddle is the safest 

 plan. 



Insecticides, or insect killing substances, may be divided 

 into two general classes ; first, the internal poisons, which 

 cause death of the insect by being eaten with the regular 

 food ; and, second, the external irritants, which act from 

 the outside, closing the breathing pores, or causing death 

 by irritation of the skin. Paris green is an example of 

 the first class, and kerosene emulsion of the second. 



PARIS GREEN. 



.. Paris green is now widely used. It is an extremely 

 powerful poison. Its active principle is arsenic, of which 

 the pure article contains from fifty-five to sixty per cent. 

 As it contains copper, it possesses some value as a fungi- 

 cide, although for this purpose it is not to be compared with 

 the Bordeaux mixture. Very little of the arsenic of Paris 

 ^reen is soluble in water, yet it is always safest to use the 

 same weight of freshly-slaked lime as of the green, when 

 applying the poison. This prevents the burning of the 

 foliage. The lime renders any soluble arsenic harmless, 

 combining with it to form the insoluble arsenite of lime. 

 Paris Green rapidly separates from the water with which 

 it has been mixed and settles to the bottom of the barrel, 



