605 The Trials of Grist Mills and Disintegrators at Plymouth. 
The Millstone (Fig. 1) is older than human history, being 
familiar to us in the quern, the Etruscan sheller, the Porn- 
peiian and Egyptian mills ; but it will' appear, later, that stones 
are not so well adapted to the purposes of grist milling as metal 
plates or rollers. 
Metal Discs (Fig. 2) were used by Napoleon on the march 
to Moscow for the purpose of supplying his troops with meal. 
The " French Military Mill," as it was called, consisted of a pair 
of cast-iron discs about 12 inches in diameter, vertically ar- 
ranged, and turned by hand — a machine similar, indeed, in all 
essential respects, to that which took the first prize at Plymouth. 
Francis Devereux patented this " Military Mill " in England in 
1824, and the recent winner may perhaps reflect, with some 
satisfaction, that " Peace with Honour " attends the latest 
triumph of a machine having forefathers born in a camp, and 
nurtured amid the clash of arms. 
Conoidal Metal Discs (Fig. 3) were invented by David 
Selden, of Liverpool, who, in 1831, took out a patent for a mill 
which worthily fathers that of Bamford and Nicholson. Indeed, 
it is a question whether it might not have gone hard with the 
descendants in question, at the Plymouth trials, could their 
ancestor have appeared there as a competitor. 
Grooved Boiler and Breast (Fig. 4). — In 1833, a certain 
Thomas Don, of Westminster, patented a vertical millstone 
which, revolving peripherally, bore against the segmental 
curve of a second stone of rather larger radius than the runner ; 
but Don was, himself, anticipated by Charles Williams, of 
South wark, who, in 1810, made a metal mill consisting of a 
grooved roller working against a breast formed of a number 
of knives, screwed together so as to form the same curve as 
the roller, the knives being removable for the purpose of sharp- 
ening. The roller in Williams's machine was kept up to the 
breast by weighted levers, which, while furnishing pressure 
enough for the purpose of grinding, allowed the breast to give 
way, exactly as in modern practice, on the passage through the 
mill of hard foreign substances. 
Conical Boiler and Breast, giving endwise delivery of Meal 
(Fig. 5). — Amory Felton, an American, seems to have been 
the first inventor, in 1855, of the horizontal conical roller and 
breast, which, first introduced into this country by Riches- and 
Watts in 1857, became a model for the well known and now 
widely distributed Barford & Perkins's gristing mill. 
Boiler Mills (Fig. C), like the millstone, are older than 
human history. Niebuhr, in 1772, described a roller mill, of 
refined construction, but of unknown antiquity as to design, 
