ROTARY BLOWERS. 227 



of material to be blown, these macbiDes may be noticed under two heads; 

 (1) Rotary fans for blowing powders and (2) Rotary fans for Mowing 

 fluids. 



The hand -blowers shown in Plate XXVIIT, Fig. 1, and those in Plate 

 XXVII, Figs. 5 and 6, 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 exiDcrieuce 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 powder.^ — In considering these, it 

 must be remembered that the poisons are commonly mixed with other 

 powders as diluents, some of which, as flour for example, refuse to flow 

 readily, and pack together over the hopper outlet to clog it, so that an 

 arrangement for feeding these more difi&cult 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, flour 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 3. 



In these Figs, it will be seen that the hopper, j?, is represented by 

 a hermetic can mounted on the blower-drum, <?, or discharge pipe, L 

 The top is closed tight, and may be opened by the large screw-cap or 

 plug, c, or by a large tight-fitting lid. Its sides are preferably vertical, 

 as shown, and the base is entirely open, as at x. Beneath the open base 

 and still larger than the same, is a hanging base or roof, &, suspended at 

 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 

 sides 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 attritional 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 smallperforations, slotted or other; 

 but the simple imperforate plate is satisfactory enough, and 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 



