EXPERIMENTS WITH DRY POISONS. 



227 



from Koyall's mixture being in omitting some ingredient, substituting 

 gypsum, bulk for bulk, for flour, or varying the quantity of poison. 



When these poisons were applied in the afternoon, the sun was shining 

 brightly. The mixture with plaster was scattered more easily than 

 those with flour, and distributed itself very evenly over the leaves. On 

 the 31st of August a few drizzling showers fell, and there were more 

 on the next day, scarcely any falling during the succeeding night, and 

 a very little the following morning. August 28, after two clear days 

 and dewy nights, I found all of these poisons adhering well; though the 

 flour, by forming a sort of paste, had collected into blotches, while the 

 plaster remained as evenly distributed over the leaf as ever. On the 

 2d of September, I noted that the cotton of section 5 was somewhat 

 scorched. Section 6 was scorched very little. Though section 7 was in 

 great part removed, it had scorched the cotton considerably ; more than 

 either of the other sections. Very few leaves were injured on section 8. 

 This same day, I found that a very little of section 1 still adhered, and 

 the cotton was little injured. A little was also found on section 2, where 

 the cotton was very little hurt. Section 3 seemed to adhere as well as 

 the preceding, but had scorched the cotton more. Section 4 had scorched 

 the cotton little, but no traces of the poison were left. 



September 2, two other sections were poisoned, using one part of flour 

 by weight to two parts of gypsum in place of an equal bulk of flour in 

 Eoyall's patent. 



* By a mistake the quantities of rosin, dextrine, and Paris green were intended for twice the bulk of 

 flour and plaster used. 



