288 TEANSACTIONS OF THE HOETICULTURAL 



(lepradations of one of the worst of insect pests. At first many ob- 

 jection vS were raised to the use of so active a poison upon garden es- 

 culents, but the experiments of eminent chemists, notably those of 

 Dr. Wm. McMurtrie, then chemist to the United States Department 

 of Agriculture, and Dr. R. C. Kedzie of the Michigan Agricultural 

 College, showing that no danger could arise from its legitimate use, 

 largely allayed the popular fear. Having proved so efficient in de- 

 stroying insects affecting potatoes, Paris green naturally came into 

 use as a remedy for other pests of similar habits, and has continued 

 to give good satisfaction in nearly every instance where the pure ar- 

 ticle is applied, though because of its high price and ready sale it is 

 very largely adulterated. 



Chemically, Paris green is a compound of arsenic and copper, 

 known as arseniate of copper, and contains, when pure, fifty-eight 

 per cent, of arsenious acid, or white arsenic. Of course for use as 

 an insecticide it is important that the article be pure; otherwise the 

 directions given for applying it will be incorrect. The adulterated 

 Paris green is generally of a lighter color than that which is good, 

 and should never be purchased. 



APPLICATION, 



Paris green, like most other insecticides, may be applied either 

 dry or wet, /. e., diluted with some powder as flour or plaster, or me- 

 chanically mixed with water. I say mechanically mixed, because, as 

 doubtedless most of you are aware, it is practically insoluble in water. 

 In general, liquid application is preferable but the user must be 

 largely governed by the circumstances of the case. As a dry diluent, 

 flour is the best substance obtainable, as its adhesiveness when damp- 

 ened aids in attaching the poison to the plant leaves. The prepara- 

 tions of the mixture vary somewhat according to relative tenderness 

 of the foliage to which it is to be applied. But in general it is safe 

 to use in the proportions of one part by weight of Paris green to 

 twenty parts of flour. For liquid application mix one ounce with 

 three gallons of water, or one pound with forty or fifty gallons of 

 water. 



LONDON" PURPLE. 



London purple is another insecticide which, though introduced 

 later than Paris green, has largely superseded it, and on many ac- 

 counts is to be preferred. Being a waste product in the manufacture 

 of aniline dyes, formerly discarded as worthless, its cost is compara- 

 tively small, only fifteen cents a pound at retail, and much cheaper 

 in quantity. Besides that just given. Dr. Lintner gives the following 

 reasons why its use is more desirable than Paris green: 



" It is of nearly uniform strength, and as its production is much 

 in excess of demand, it does not pay the manufacturer to adulterate 

 it by mixture with any other substance. As mixed for use it is far 



