ROTARY BLOWERS. 
227 
of material to bo blown, these machines may be noticed under two heads; 
(1) h'otary fans for blowing powders and (2) Rotary fans for blowing 
fluids. 
The hand blowers shown in Plate XXVIII, Fig. 1, and those in Plate 
XXVII, Figs. 5 and G, have proved the most satisfactory that I have 
devised. Of those invented by others, none have yet proved to be very 
practical or successful for field usage. My experience indicates that 
the oscillating bellows blowers, with the improvements described below, 
are preferable to rotary fans, but that the latter may yet take a high 
rank. 
ROTARY fans for blowing powdkk. — In considering these, it 
must be remembered that the poisons are commonly mixed with other 
powders as diluents, some of which, as Hour for example, refuse to flow 
'readily, and pack together over the hopper outlet to clog it, so that au 
arrangement for feeding these more dillieull substances as well as the 
poisons proper is necessary. The various forms of hoppers used in ma- 
chinery are not satisfactory for the slightly adhesive or cohesive sub- 
stances which it has generally been found desirable to use. If a hopper 
has an inclined or horizontal perforated base, even with a very large 
hole, or if its sides are not vertical, but sloping, Hour will not slide down 
and out in a steady satisfactory manner, even when subjected to the 
ordinary jolting of a machine hauled upon the ground. A simple hop 
per that I have contrived for dry poisons and their mixtures, to feed any 
amount desired, and to do it regularly without clogging, is represented 
in plan sections in Plate XXVIII, Figs. 1, 2, and «'5. 
In these Figs, it will be seen that the hopper, |>, is represented by 
a hermetic can mounted on the blower-drum, r/, or discharge pipe, i. 
The top is closed tight, and may be opened by the* large screw-cap or 
plug, c, or by a huge tight-fitting lid. Its sides are preferably vertical, 
as shown, and the base is entirely open, as at .'. Beneath the open base 
and still larger than the same, is a hanging base or roof, suspended ;it 
its ends by bolts, each through a short tube, /, and with a thumb-nut 
above by which to elevate or lower it. Whether this be suspended in 
the upper part of a blower-drum or of a spout, the blast can act at its 
sales and above it along the slot like openings where the powder rests 
exposed. The mass of powder and its hanging base can be set deeper 
or less deep into the blast passage, thus choking it more or less and 
increasing or diminishing the atrritional power and wearing surface 
whence the blast feeds itself. As the mass of powder thus tends to be- 
come undermined more and more, it sinks without clogging or interrup- 
tion down onto the hanging base, which may be flat or bent throughout 
or at its margins. It can also have small perforations, slotted or other; 
but the simple imperforate plate is satisfactory enough, aud will proba- 
bly prove the best and standard form to use. So it will be seen that by 
setting the base nearer or farther from the powder-blast the quantity 
may be gauged, and since flour adheres to the straight metal walls of the 
