The Trials of Grist Mills and Disintegrators at Plymouth. 621 
occurred. Two concaves of ^-inch mesh and two of j-inch mesh 
were employed in bone-grinding, and the sample produced was 
very good. 
The machine was tried a second time upon cotton-cake, of 
which 4 cwt. was ground at the rate of 20 cwt. per hour ; but, 
again, with a large comparative expenditure of power. Grids 
of £-inch mesh were employed, and the sample was good but 
dusty. 
The trial of Messrs. Hall, Robinson & Co.'s machine 
(No. 3479), which is a rather roughly made reproduction of 
the Harrison Carter mill, already described, ended in a com- 
plete fiasco. Within five minutes of starting on his pre- 
liminary run, his strap, which from the first was mutinous, 
broke, and some changes, involving the free use of saw and 
axe, had to be made in the platform supporting the mill before 
this could start again. Difficulties with the strap recurred on 
starting a second time, nor could the efforts of two men, 
coaxing the belt with hammer shafts, induce the latter to keep 
on the pulley. Meanwhile, the machine refused to receive any- 
thing but the smallest pieces of bone, which were pushed, either 
by means of a stick or the feeder's hand, in a most dangerous 
way, into the body of the unwilling disintegrator. All large 
bones were rejected, and the rate of feeding was extremely 
slow. Before the operator had got through a fourth of his 
" preliminary " bones, the fast-slackening strap again rebelled, 
and attempting, in spite of hammer shafts, to mount, now the 
bearing, and now the body of the machine itself, finally struck 
work for the third time, and thus brought the " trial " to a close. 
Messrs. W. N. Nicholson & Son's "Bone Mill and Dis- 
integrator" (No. 3331), which took the Second Prize, was the 
next machine tried. It consists of two pairs of toothed grinding 
rollers, one of coarse and one of finer pitch, set one above the 
other, an arrangement so well known in bone and cake mills 
as to need no further description. The mill is well and strongly 
made of the best materials and workmanship, while the roller 
adjustments, together with the provisions for allowing hard 
foreign substances to pass, are well considered -and effective. 
The grinding rollers consist of separate discs of cast steel, 
which are interlocked one with the other for the purpose of 
diminishing galling of the square driving shaft, upon which the 
discs are loosely threaded. This bone mill occupies an over-all 
floor-space of G feet x 5 feet 6 inches, and weighs 28 cwt. It 
is driven by belting direct from the motor, the necessary 
reduction of speed in the crushing rollers being provided for 
by self-contained gearing, 
