69 
spring to baits prepared for this purpose. As the beetles hi- 
bernate in last year’s potato fields, such baits should be 
laid in them. All that is necessary is to pile up in such 
fields small heaps of potatoes, or potato peelings, to attract 
the hungry insects. If these potatoes are thoroughly poisoned 
with Paris-green or London-purple, we have a bait which will 
both attract and kill. 
Asa general rule farmers are altogether too liberal with 
Paris-green and London-purple, and if it were not for the fact 
that the potato-plant can stand a vast amount of such poison, 
farmers would do much more harm than good by using these 
poisons in the manner in- which they are doing now. A small 
amount of poison uniformly spread over the plant is what is 
required and if more is used, it is simply thrown away. 
Every potato-grower ought to have in his possession a good 
spraying machine, as sucha machine is useful not only against 
insects and vegetable diseases, but also for various other pur- 
poses. Nor is itnecessary to spend much money for such an 
outfit, as there are many cheap machines on the market, which 
are at the same time very effective. In using arsenical poisons 
such as Paris-green, London-purple, or white arsenic, the fol- 
lowing rules should be keptin mind: these three substances are 
mineral compounds of arsenious acids, and consequently very 
poisonous to all organized matter. To use them properly we 
must recollect that plants can be poisoned by them as well as 
animals, and that they have to be diluted in certain propor- 
tions with other substances to make them harmless to plants, 
and yet keep them poisonous enough to kill such insects as 
eat the foliage covered with them. 
PARIS GREEN. 
Paris-green is a chemical combination of arsenious acid and 
copper, and is called by chemists arsenate of copper. It con- 
tains, when pure, about 58 per cent. of arsenious acid. Pure, 
it is insoluble in water, and can be applied either asa dry pow- 
der mixed with other substances, or suspended in water. As 
plants are affected in different degrees by this poison, the ex- 
act proportion of it and dilutants can not be given, except in a 
general way. Some plants, as the potato, can be dusted with 
quite a large amount of it without being greatly injured, while 
