No. 4.] INJURIOUS INSECTS. 147 



suspension in the water much longer than Paris green ; that 

 it is white in color and can be readily seen on the leaves, so 

 that one can tell at a glance what has and what has not 

 been sprayed, which is often a great convenience ; but the 

 greatest advantage is that it does not injure the foliage, even 

 when used in as large proportions as twenty-five pounds or 

 more to one hundred and fifty gallons of water. Many 

 people object to the use of Paris green, as it so frequently 

 injures the foliage. This is undoubtedly because they use 

 too large a proportion, or else they do not keep it properly 

 stirred all the time it is being sprayed on the plants. No 

 such trouble arises in the use of arsenate of lead, but it 

 should be constantly stirred during the spraying, to secure 

 an even distribution of the poison on the plants. 



Several persons have reported to me that they have seri- 

 ously injured their plants by the use of arsenate of lead 

 when they followed the rule given in the above-mentioned 

 bulletin. This rule was to put eleven ounces of acetate of 

 lead and four ounces of arsenate of soda into a hogshead 

 containing one hundred and fifty gallons of water. In one 

 of the cases the man acknowledged that he reversed the 

 proportions, and used eleven ounces of arsenate of soda and 

 four ounces of acetate of lead. No Avonder the leaves were 

 burned. There were others, however, who found that 

 arsenate of lead burned the leaves even when the proper 

 proportions of the ingredients were used. In this case I 

 imagine that the arsenate of soda was put in first and dis- 

 solved, and then when the acetate of lead was put in the arse- 

 nate of soda at once formed a surrounding layer of arsenate 

 of lead, which, being insoluble, prevented the interior mass 

 from dissolving, and thus a large quantity of arsenate of 

 soda remained in the water, and when sprayed on the trees 

 would surely burn the foliage. To avoid all such difliculty 

 I would now recommend that eleven ounces of acetate of 

 lead be put in four quarts of water in a wooden pail, and that 

 four ounces of fifty per cent arsenate of soda be put in two 

 quarts of water in another wooden pail, and, when they are 

 entirely dissolved, pour each of them into a hogshead con 

 taining about one hundred and fifty gallons of water, when 



