736 
Report on the Exhibition of Implements^ 
raised and reground. There is much merit in this machine ; the 
wearing parts are not liable to serious wear, and renewals can 
be made with facility. The way in which the action is ob- 
tained is ingenious. This combines the blow of the stamper 
with the triturating action of the pestle. The position of the 
mill inside its own sifter is also a great advantage, as it ensures 
the delivery of a completely prepared article. Another point, 
upon which some stress is properly laid, is that the powdering 
action does not depend upon the momentum of the substance to 
be powdered, but that it is actually pounded and rubbed be- 
tween surfaces of chilled iron and steel. As compared with 
Fig. 29. — Sedimnl Yieic of Thomjmm's Patent Comminutor. 
edge runners, the Concessionnaires declared that the commi- 
nutor shows a large increase in the out-put for the horse-power 
employed. And as regards horizontal stones, there is the entire 
saving of dressing, and greater results with half the horse-power 
required for grinding. The claims are : — 
1. That the mill can be run at a comparatively slow speed, 
and therefore wear and tear is reasonable. 
2. That the grinding and sifting are thoroughly done at one 
operation. 
3. That the wearing parts are easily renewed when required. 
The ball, the path on which it travels, and the discs, are made 
of hard chilled iron. The ball by rolling wears itself true, and 
