SPEAYISrO FOE INSECTS AKD FUNGI. 143 



purple lies in tlie arsenic it contains, just as in the case of 

 the Paris green. There are, however, several advantages 

 possessed by the new poison over the old, among which 

 are: (1) its extreme fineness, permitting it to be mixed 

 with water; (2) its adhesiveness: when once applied it 

 adheres tenaciously to the leaves; this is due no doubt to 

 its finely divided condition; (3) its purple color enables 

 one always to detect its presence on leaves even when it 

 exists in very small quantity; this will not only guard 

 against accidents,, but at the same time be of considerable 

 account in enabling one to always know when it is neces- 

 sary to make another application; (4) its cheapness as 

 compared with Paris green." 



At that time Hon. John IST. Dixon, of Oskaloosa, Iowa, 

 was a trustee of the Iowa Agricultural College and was 

 the owner of one of the largest apple orchards in the State 

 at that time. The canker-worm visited this orchard in 

 1877. In 1878 he reported as follows in the lotva Horti- 

 cultural Report : " My success with these chaps has been 

 so encouraging that I am very willing' to talk about it. 

 I mix a pound of arsenic in one hundred and fifty gallons 

 of water, heated in a sort of sorghum-pan concern got up 

 for the purpose. I dissolve the arsenic by boiling in much 

 stronger proportion than this, but I am careful to add 

 water when the liquid is put in the barrels for use, so as 

 to make the proportion as above stated. The pump I use 

 for throwing the water over the trees cost, in Chicago, 

 sixteen dollars. I load the barrels of water in a wagon 

 and drive on the windward side of the row to be sprinkled. 

 I find I can thoroughly poison the foliage by showering 

 from the one side. I first tried the Paris green, but found 

 it expensive and liable to burn the leaves; it is also a 

 dangerous stuff to use. The arsenic water makes a deli- 

 cate coating of arsenic over the leaves, but the rains soon 



