REPORT OF THE ENTOMOLOGIST. 317 



more easily than that of some other plants, and also that a substance 

 may kill certain insects quickly while it acts much more slowly upon 

 others. London purple consists chiefly of arseniate of lime, together 

 with considerable anihne purple, and a little impurity. As it is a waste 

 product in the manufacture of various salts of rose aniline, its compo- 

 sition is not constant. A sample which was analyzed by Dr. Collier 

 shows the following composition : 



Per cent. 



Rose aniline - 12.46 



Arsenic acid 43.65 



Lime 21.82 



Insoluble residue.--. 14. 57 



Iron oxide 1.16 



Water 2.27 



Loss 4.07 



100.00 



A compound of arsenions acid and cyanide of potassium has been 

 used to a considerable extent in Texas. It is known as Johnson's Dead 

 Shot. It was patented June 2, 1874. The following extract from the 

 specifications, describes the compound : 



In order to form ray compound I use the following ingredients, and preferably in 

 the following proportions, to wit: Eight ounces of arsenions acid, one ounce of cyanide 

 of potassium, and eight ounces of dextrine, dissolved in forty gallons of water. 



Arsenious acid, when applied to the leaves of cotton or other plants in the form of 

 spray, will remain free from evaporation for a sufficient length of time to be eaten by 

 Buch insects as feed upon cotton or other plants. Cyanide of potassium, when applied 

 in like manner as a component part, might be termed the base of said compound, and 

 serves to hold the arsenious acid in solution before it is conveyed to the plant, and, 

 being among the most deadly of all insect poisons, it not only kills when eaten, but 

 is death to insects the instant it strikes them, and so impregnates the air immediately 

 around the plant upon which it has been deposited that the fly or miller which creates 

 the cotton-worm is instantly killed on coming in contact with, or in the immediate 

 vicinity of, the same ; and, being a powerful alkali is easily, absorbed by vegetation, 

 and acts as a tonic or fertilizer, thus entirely neutralizing the evil or damaging effects 

 of the arsenious ingredient upon both land and plant. Dextrine, one of the component 

 parts of my compound, has no poisonous effect, but is simply used to produce a thin 

 mucilage of my other ingredients, sufficient to hold the said compound on the plant 

 to which it may be administered. 



Xo experiments were tried with this compound. We have no doubt, 

 however, that it is effectual as an insecticide ; but we would hesitate to 

 recommend the use of a volatile poison so deadly as cyanide of potas- 

 sium. 



Objections to the use of arsenic and its compounds. — Much has been writ- 

 ten respecting the dangers attending the use of arsenical poisons as in- 

 secticides. We do not here refer to the caustic action of the poison upon 

 the leaves of the plant, but to the injuries which may result to man 

 from the incautious handling of so deadly a poison; to animals by drink- 

 ing water from vessels in which it has been mixed, and by drinking 

 from streams flowing through cotton fields thus treated, and espec- 

 ially to the danger of the poison accumulating in the soil to such an ex- 

 tent as to exert an injurious influence on the plant. When we consider 

 the immense quantity of this poison which has been used during the 

 last few years, and the low grade of intelligence of the majority of the 

 field-hands who have been required to apply it, especially in the cotton 

 States, it seems as if a great risk of loss of life had been incurred ; 

 statistics, however, fail to confirm such conclusions. We occasionally 

 read in the newspapers accounts of serious results following the use of 

 poisons as insecticides, but no well-authenticated case has come to our 

 notice. Althougli, doubtless, there is danger with the usual care, the 



