INSECTICIDES, PREVENTIVES, AND MACHINERY. 437 



hundred gallons ready for use. This combination has the ad- 

 vantage of being harmless to foliage, whatever the strength in 

 which it is applied. The fifteen ounces of mixed arsenate and 

 acetate have been applied to peach-trees in two gallons of water, 

 and this — the most dehcate and sensitive of all fruit-foliage — 

 was absolutely uninjured. The mixture is less poisonous than 

 either Paris green or London purple, containing, as it does, a 

 smaller percentage of arsenic in an absolutely insoluble form ; 

 but it is also much cheaper, and to obtain the same effects costs 

 just about the same, or a trifle less. As a rule, four ounces of 

 arsenate of soda and eleven ounces of acetate of lead will suffice 

 for one hundred gallons of water, and this mixture will be effec- 

 tive against most insects, including the elm-leaf-beetle in all its 

 stages, the various w^eb-worms, canker-worms, and the codling- 

 moth. Where a rapid effect is necessary, the quantity can be 

 doubled. Where a great deal of the mixture is to be used, it 

 can be made in a concentrated form, and a proper proportion of 

 the stock added to each tank of water as used. Arsenate of 

 lead does not dry, but forms an almost pure white, pasty pre- 

 cipitate. It remains well in suspension, and needs but little 

 stirring. Its great advantage is its harmlessness to plant-life of 

 all kinds. It should not cost above eight cents per pound for 

 arsenate of soda and fourteen cents per pound for acetate of 

 lead, or about thirteen cents per fifteen ounces for the arsenate 

 of lead. 



Pure white arsenic has been recommended, and is used with 

 satisfaction by some agriculturists. It is certainly the cheapest 

 as well as the most active of the poisons of this class. It is effec- 

 tive at the rate of one pound in from two hundred and fifty to 

 five hundred gallons of water, the latter strength corresponding 

 to Paris green at one pound in two hundred gallons, and the 

 former to one pound in one hundred gallons. It contains much 

 more soluble arsenious acid than either of the other mixtures, and 

 will burn foliage severely unless mixed with twice its own weight 

 of quick-lime. If that be done, however, an insoluble arsenite 

 of lime is obtained which is exceeding effective and can be used 

 as safely as any of the other mixtures. 



There is sometimes a Httle difficulty in making a water mixture 

 stick to very smooth, or spread over very hairy leaves, and in 



