144 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
chine and the labor. Both of the last two items are extremely variable, 
and it is difficult to get at the average cost. One of the improved 
sprinklers will cost, on an average, say, $15, and will last for several 
seasons with but little expenditure for repairs. Two hands are neces- 
sary to operate the machine. One hundred acres of cotton can be 
poisoned in a day by these two men with one machine, 16 pounds of 
Paris green, and (not absolutely necessary) a small amount of flour and 
ashes. 
This dry method of applying Paris green has proved satisfactory 
under the conditions already referred to whenever a genuine article 
has been obtained and properly applied. Eeported cases of failure must 
be attributed to adulterated poison, or to the use during very wet 
weather of ingredients of inferior quality. The proportion of the green 
to the ingredients actually in use in the South varies from 1 pound of 
the green to 20 pounds of ingredients, to 1 pound of green to about 35 
pounds of ingredients, the stronger mixture being generally adopted in 
Texas, the weaker in the more eastern portion of the cotton belt. This 
great difference is partially explained by the fact that the mixture is as 
a rule more economically applied in Texas than further east. The origi- 
nal idea was to distribute 1 pound of the green over one acre of cotton 
of average size, and by a very slow and careful manipulation of the 
sieves it is indeed barely possible to accomplish this satisfactorily if 20 
jiounds of ingredients are added. Practically, however, the amount of 
the mixture used per acre always exceeds 30 pounds, and often reaches 
50 pounds or even more. This great waste is the necessary consequence 
of the imperfect implements that have been employed so far, and par- 
tially also of the carelessness of the hands. The small tin sieves so ex- 
tensively used in the cane -brake region of Alabama are especially waste- 
ful in the distribution of the mixture, and onebarrel (almost 200 pounds) 
is, on some plantations, not expected to go over much more than three 
acres. That 1 pound of the green to 30 pounds of diluents applied at 
the rate of not more than 20 pounds to the acre is efficient has been 
proved by actual experience over and over again, and all stronger ad- 
mixtures of the green should, therefore, be abandoned. But in every 
application of this mixture during dry weather another point of still 
greater importance can be learned : Wherever the mixture is applied 
very slightly, so as to be a mere dusting of the leaves, it is fully as effi- 
cient as where it thickly covers the plant. One of the chief aims we 
have had in mind has been to ascertain by experiment the minimum 
quantity of the poison that could advantageously be used, and Mr. 
Schwarz was intrusted with experiments in this direction. He reports 
as follows; 
u Minimum quantity of Paris green. — That the method of applying dry 
poisons by means of common bread-sieves, and still more by means of 
small tin sieves, is a very wasteful one, needs no further remark, and a 
