OBJECTIONS TO THE USE OF ARSENIC. 235 



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 ; statis- 

 tics, 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. Al- 

 though, doubtless, there is danger with the usual care, the risk is not 

 greater than that of railway or steamship travel or. many other practices 

 which are necessary. 



These remarks will apply also to the dangers accruing to animals from 

 this use of poison. For, although we are informed that the annual loss 

 by Paris green of cows, sheep, and horses is something considerable, no 

 instance has come under our personal observation. 



As to the accumulation of the arsenic in the soil, in sufficient quantity 

 to prove injurious to plants, we cannot do better than to cite the inves- 

 tigations of Dr. William McMurtrie.* These investigations show: 



That, though arsenical compounds exert an injurious influence upon vegetation, yet 

 this is without effect until the quantity present reaches, for Paris green, about 900 

 pounds per acre ; for arsenite of potassa, about 400 pounds per acre. 



Thus, if all the arsenic were to remain in the soil no injurious effects 

 need be expected to follow within one hundred years. And when we 

 take into consideration the amount of arsenic which is removed from the 

 soil by drainage, an even greater time may be expected to elapse before 

 that event occurs. And we may reasonably expect that ere that time 

 the science of economic entomology will be so far advanced that a harm- 

 less substitute for arsenic will be known if there remains an occasion for 

 its use against this enemy of the cotton plant. 



Carbolic acid. Experiments conducted by Professor Willet and my- 

 self last season with carbolic acid gave results similar to those obtained 

 by Mr. Trelease. It was found in each case that where this substance 

 was used in sufficient quantities to destroy the worms it injured the cot- 

 ton plants greatly. 



Kerosene. Although the different forms of coal-oil have been found 

 to be very valuable in many instances as insecticides, all of our efforts 

 to employ it against the cotton-worm have produced poor results. In 

 every case when a mixture of kerosene and water of sufficient strength 

 to destroy the worms has been applied to cotton, the plants have been 

 injured. 



The following experiment, suggested by the use made of kerosene 

 "Annual Report of the Department of Agriculture, 1875, pp. 144-147. 



