18 INTRODUCTION. 



dry or wet. In the former case it should be well 

 mixed with some fine powder as a diluent : plaster, 

 air-slaked lime, flour, road-dust, and finely-sifted 

 wood ashes, all answer the purpose fairly well, though 

 lime or plaster are usually preferable. The propor- 

 tion of poison to diluent varies greatly with different 

 users — one part poison to fifty, and even one hun- 

 dred, of diluent, will usually be effective, if the 

 mixing be thoroughly done. In the wet mixture, for 

 fruit and shade trees, use one pound poison to 250 

 gallons of water, and keep well-stirred. The chief 

 objection to Paris green is that it is so heavy that it 

 settles quickly to the bottom of the vessel — very 

 much more quickly than London purple. It is also 

 more expensive. 



London Purple is a by-product obtained in the 

 manufacture of aniline dyes. It generally contains 

 nearly the same percentage of arsenic as Paris green, 

 which, however, is often in a more soluble form, and 

 consequently it is more liable to injure foliage than 

 Paris green. It is a finer powder than the green, and 

 hence remains in suspension in water much longer. 

 It is also cheaper, retailing at about fifteen cents per 

 pound. It may be used in the same way — as a pow- 

 der or in water suspension — and the proportions 

 given above answer very well for it. But i* should 

 never be applied to plants having a foliage easily 

 injured by these arsenites, like the peach or plum, 

 Paris green being preferable for this purpose. 



White Arsenic is sometimes recommended as an 

 insecticide, but, fortunately, is rarely used. It is much 



