152 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
also in very dry weather, the proportion of £ pound to 18 of the dilu- 
ents is most to be recommended. This refers to very economical appli- 
cation by means of a careful handling of the sieves. As the sifting is 
generally done less economically, the following proportion is to be 
recommended : One pound of the purple to about 45 pounds of diluents, 
the latter most advantageously consisting of 15 pounds of wood ashes 
and 30 pounds of flour, including the usual amount of adhesive mate- 
rials. This would give about 4 pounds of the purple to 1 barrel of flour. 
As to the cost per acre of cotton, the remarks made under the head of 
Paris green also hold true here, the low price of the purple rendering 
its api>lication of course so much cheaper. 
The experiments made by the agents of the Commission in applying 
the purple without diluents have completely failed for want of machines 
wherewith to apply evenly the very small quantity of the poison re- 
quired for each plant, the results invariably being that the leaves were 
considerably scorched. The invention of machines bringing about the 
even distribution of very small quantities of poison will naturally open 
a wide field for further experimentation. That even a very slight dust- 
ing with the purple mixture mentioned above is fully efficient has been 
proved by the experiments made in Texas in 1879 ; but such economic 
application is impossible on a large scale, so long as we cannot dispense 
with the sifting methods. 
Wet application. — Like Paris green, it is not soluble,* but is much 
easier kept suspended in water than the former. If applied in this way 
some care has to be taken in stirring it in the water, as it has a tendency 
to form lumps, owing to its finely-powdered condition. Experiments 
on a large scale with this material diluted in water gave the following 
results: When used in the same proportion as Paris green, namely, 1 
pound of the poison to about 40 gallons of water, one experimenter 
reports that the leaves were slightly crisped, while four others report 
perfect success, and no injury whatever to the plant. Experiments by 
ourself and Mr. Schwarz in the year 1879 showed that when applied 
iu the proportion mentioned and thoroughly stirred up in the water the 
leaves were partly crisped, though by no means so much as by arsenic, 
even when applied in weaker solution. When used in smaller propor- 
tion, or at the rate of f or J pound to 40 gallons of water, it did not burn 
the leaves, and still proved effectual in destroying the worms. Re- 
peated experiments on a smaller scale confirmed these results obtained 
on large fields, and also showed that the proportion may be still farther 
reduced, and when applied with great care and in very dry weather i 
pound to 40 gallons will kill. Still farther reduction in the proportion 
of the powder used gave negative results. 1 would therefore recom- 
mend the use of J pound of this powder to from 50 to 55 gallons of 
water as the proportion most likely to give general satisfaction by 
effectually destroying the worms without injuring the plants. 
* The manufacture™ can render about 13 per cent, of it soluble if desired. 
