OSCILLATING BLOWERS. 
235 
"Aside of the circumstance that only two rows of cotton are supplied 
at once with vapor, it is very doubtful whether the worms are killed by 
sulphur vapor in the open air, judging from its effects on other insects 
when not confined." 
Until some kiud of vapor that is practically effective for application 
in the open air becomes discovered, it will not be worth while to occupy 
time and space with vapor-machines for such purposes. 
Force blast rotary blowers are made for forges, &c, but none 
has been found cheap enough and otherwise adapted for poisoning- 
machines. Should such be made, they would probably supersede the 
ordinary rotary fan blowers, and, perhaps, the oscillating bellows. 
OSCILLATING BELLOWS BLOWERS OF POISON. 
[Plates XXX to XXXV.] 
In considering this group of blowers the more important general re- 
sults of my study and practical experience with them will be presented 
at once and thereafter descriptions of a few of the machines. The word 
bellows is sometimes applied to rotary fans and to reciprocative piston 
blowers; but the common oscillating leather bellows of our forges are 
examples of the kind to be specially noticed in this snbseetion. These 
are much more powerful instruments than the rotary fans for blowing 
powder into the state of finely diffused clouds, or for blowing liquids 
into atomized sprays, while they can also be used to produce an air- 
pressure in tight reservoirs to force out the liquid contained, whereby 
a<Htilizable squirting power is afforded, but almost do pressure at all 
can be produced with the rotary blowers. Also, these are generally 
preferable to the latter, because less costly, less complicated, and re- 
quiring little velocity, while they allow almost no waste of energy in their 
operation, are light, and their blast can be conducted great distances 
through very small tubing, much less cumbrous than the large spouts 
of the rotary blowers. 
Those specially interested in blowing poison should read carefully 
what follows with reference to the figures of Plates XXXI, XXX II I, 
ami XXXI V. 
A main drawback to these bellows has been in the difficulty of con- 
•tractiog them to endure exposure to the wetness of field-work, but 
this matter is entirely corrected in the strong, cheap bellows here rec- 
ommended. 
These have the heads of wood or sheet-metal and about equal and 
rounded in outline, while each has a groove in its periphery, into which 
the stout leather is drawn tightly by thick nealed wire. Thus the leather 
is held mechanically without needing paste, glue, or nails, and the bellows 
is constructed more strongly, quickly, and cheaply. The heads are pre- 
ferably of metal, as wood is apt to cause leakage from shrinking or 
cracks. There is no seam in the leather, which only overlaps broadly, 
making it of double thickness to act as a hinge on one side where the 
two heads of the bellows come together. The incurrent orifice and valve 
