OSCILLATING BLOWERS. 235 



"Aside of the' circumstance that ouly 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 kind 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 i)robably supersede the 

 ordinary rotary fan blowers, and, perhaps, the oscillating bellows. 



OSCILLATING BELLOWS BLOWERS OF POISON. 



[Plates XXX to XXXV.] 



In considering this grouj) of blowers the more imi)ortant 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 subsection. 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^ atilizable squirting power is afforded, but almost no 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, XXXIII, 

 and XXXIV. 



A main drawback to these bellows has been in the difficulty of con- 

 structing 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 



