272 INSECTICIDES, FrXGICIDES, AND WEED KILLERS. 



emerald green into a paste. A finely divided precipitate is thus 

 obtained which keeps in suspension and allows the insecticide to be 

 evenly distributed. The best all-round proportions are 0-08 per cent 

 of copper arsenite and 0-08 per cent of lime (8 lb. per 1000 gals.). 

 From 3-5 hectolitres of this bouillie are sprayed per hectare (26-4-44 

 gallons per acre). Spraying should be done in dry w^eather without 

 dew and renewed if rain washes the leaves before the insecticide has 

 acted, that is to say, within twenty-four hours. In arboriculture, to 

 obtain the object in view it is necessary to make three to six sprayings 

 per annum. These should be made at epochs determined by the habits 

 of the insect to be overcome. 



Precautions. — By an order of 1846 the use of arsenites 

 for the destruction of insects was forbidden in France. But in 

 spite of that injunction, owing to the success obtained in America 

 with these insecticides, their use has extended in France. Arsenites 

 are true poisons which should be guarded against ; however, by operat- 

 ing with precaution the treatment ceases to be dangerous. But the 

 operator, after the operation, should wash himself conscientiously, 

 face and hands, and brush his clothes. He should never forget 

 that he is working with a poison. It has been objected, and still is 

 objected in France, that their use on vegetables and on fruits is a 

 danger to the public health. However, in America, where this treat- 

 ment is practised everywhere no case of poisoning has been reported. 

 The Americans have seriously examined this drawback and made 

 numerous analyses of fruit and vegetables treated with arsenite, but 

 found that the poison does not enter into the plant treated, and that 

 remaining on the surface completely disappears after twenty to twenty- 

 four days. The amount of arsenic spread on plants is so minimum 

 that if they were consumed even shortly after treatment it would re- 

 quire an exceptionally large quantity to produce a poisonous effect. 

 From the analysis of the cabbages treated, Gillette calculated that a 

 person would require to eat 28 heads in a single meal to feel the 

 symptoms of poisoning. In the same way, Riley from experiments made 

 on potatoes so treated, calculated that one would require to eat several 

 26 gallon barrels to be poisoned. Three weeks after the first treatment 

 Fletcher by analysis found no trace of arsenic on the apples. Plants 

 intended for consumption do not therefore present any danger to the con- 

 sumer after that lapse of time. However, if such treatment be applied 

 in hot countries prudence must be exercised, for the absence of summer 

 rains might render the presence of this poison on the edible parts of 

 the plant dangerous. Moreover, its use must be avoided during 

 flowering, for the bees and insects indispensable to the fertilization of 

 the flowers risk being killed ; further, practice has shown that flowers 

 are rendered sterile if this treatment is applied at the time of 

 blossoming. 



Arsenical treatment is excellent when applied on vegetables which 

 are not to be consumed immediately and in countries where frequent 

 rains remove all trace of the poison. 



The profit is considerable, for no treatment is more advantageous 

 to the plant. The following figures published in America refer to- 



