Page:Popular Science Monthly Volume 42.djvu/667

 Rh commonly in use, is done with proper reference to the time, methods, and conditions of treatment, there is no danger to the consumer. Both practical experience and chemical tests have repeatedly shown that apples sprayed early in the season with Paris green or London purple retain none of the poison at the time of ripening. The most recent demonstration of this appears in the last report of the experimental farms of Canada. A peck of Rhode Island greening apples that had been sprayed twice with Paris green (one pound to two hundred gallons of water) were carefully gathered, without rubbing, and tested for arsenic. "The process to which they were submitted is one that affords extremely accurate results, and is considered the most delicate of all for the detection of arsenic. It is capable of revealing the presence of one fifty-thousandth part of a grain of arsenic. If twenty-three thousand bushels of apples contained two and a half grains of arsenic, the minimum fatal dose for an adult, the poison could have been detected by this method." Notwithstanding the most careful analysis no traces of poison were found; and, in conclusion, the chemist states: "I am of the opinion that further experiments of this nature would only serve to corroborate this negative result, and to prove that there are no grounds on which to base a suspicion that our sprayed apples are poisonous. The insoluble character of this poison precluding its assimilation by the apple, if such were possible, the infinitesimal part of Paris green that can remain on the apple, the frequent rains subsequent to the spraying, . . . all go to substantiate the argument that there is not the slightest danger of poisoning in using sprayed apples."

There is abundant evidence of a similar nature concerning the use of copper salts on grapes. In France, where a large proportion of the grape crop is converted into wine, elaborate investigations have shown that practically none of the copper salts are present in wine from sprayed vineyards. Prof. B. Fallot, of the School of Agriculture at Montpellier, in recording the results of one of these investigations, says: "The figures obtained have proved once more that wines, after the grapes have received numerous treatments with large quantities of salts of copper, contain scarcely a trace of this substance, and are entirely harmless."

Such is a meager and imperfect outline of this most recent improvement in the art of agriculture, which I have ventured to call an agricultural revolution. This improvement has been brought about by the combined efforts of the entomologist, the botanist, the chemist, the mechanician, and the agriculturist. Every step forward has been the result of careful study and experiment, and the whole subject is a striking illustration of the practical benefit agriculture may derive from scientific investigation and systematic experimentation.