GRAVITATIONAL ; SIFTERS. 303 
poison. With most of them there is tlie difficulty that they clog or do 
not sift regularly, especially when they are affected with wetness, which 
will generally occur, for the best time to apply the dry poison is 
when the foliage is damp enough to make it adhere. Also the adhesive 
diluents, as Hour, &c, which it is advisable to add to the poison increase 
the clogging much under the influence of moisture. On the other hand, 
when there is dryness there generally exists a little wind which prevents 
the fine powder from gravitating regularly from the sieve to the plants. 
The powder is better thrown by some device that will give it consider- 
able impetus, and on this account the centrifugal force from whirling- 
brushes or the blast from a bellows or pomp or rotary fan-blower is 
preferable. Such impetus will make it penetrate more firmly into the 
rough surfaces of the foliage or into the moisture upon the plants, and, 
to some extent, resist moderate breezes. The operation of the latter 
machines is also less affected by moisture. Although sifters may not 
be recommended generally, it is necessary to notice briefly what has 
been done toward the application of sieves to the purposes of poisoning. 
With sifters there is also probably more danger of the laborer getting 
poisoned than with machines of any other class. Where a blast or squirt- 
Log power is used the poison can be directed away from the operator 
with some force, or be discharged from a pipe extending to a sale dis- 
tance from him, but with sifters the line powder follows the caprices of 
the wind, and even with a gentle breeze there constantly exists on the 
leeward side of a person a varying weak whirlwind, hut one which 
is strong enough to lift some of the poison to his face and cause it to he 
inhaled. It was probably on account of this difficulty that Mr. -I. YY. 
Young patented, m combination with his machine described below, a 
screen to come between the sifter and the person using it. 
Reciprocating- sieve MACHINES, — With these the sieve itself is 
operated by a back-and-fortb movement. 
Concerning the method of poisoning with the simplest hand-sifters, 
Mr. William Trelease has reported as follows in the Department Report 
on Cotton Insects (p. 221) : 
k ' My dry poisons were applied by a sieve made of a 2-quart tin bucket, 
the bottom of which was replaced by perforated tin, and which was pro- 
vided with a socket at the side for the insertion of a wooden handle 
about 3 feet long. 
"My experiments with dry poisons were not extensive enough for me 
to determine accurately the amount of labor required to poison an acre; 
but Mr. lade, the manager of George O. Baker's plantation at Selma, 
Ala., tells me that a hand can poison from 1 to 2 acres of cotton per 
day. lie tells me, further, that one barrel of Royall's mixture goes over 
about 3 acres." 
Thus it is seen that the work with such a tool is very slow, and can 
only be admissible for very small patches or in an emergency where bet- 
ter means are not obtainable. 
