The Trials of Grist Mills and Disintegrators at Plymouth. 607 
in common use among the Arabs ; and Livingstone speaks in 
praise of the flour produced by a rude roller mill, also of 
unknown antiquity, in use among certain African tribes. One 
Isaac Wilkinson patented in England, in 1752, a plan of crush- 
ing grain by smooth metal rollers, and, so far as oats are con- 
cerned, the method is very extensively used to-day, although 
rollers — like millstones, as will presently more clearly appear — ■ 
are inferior to disc- and breast-grinding for the purpose of grist 
milling. 
The Plymouth trials may be regarded as an attempt to 
select from among modern improvements upon the six vener- 
able systems of grinding above described that which is best 
fitted for a farmer's use ; and it is matter for congratulation that, 
having regard strictly to this problem, the experiments gave no 
uncertain sound in declaring that flat metal discs have the 
greatest general adaptability for grist milling, while they are 
economical of power and time, produce good feeding samples, 
and are cheaper both in first cost and renewals than any other 
mills. 
But if no "uncertain sound" proclaimed the first prize 
machine, it is only fair to state the actual relationship of merit 
in which the first three mills, say, stood to each other after 
trial. The plan of judging by " points of merit," when strictly 
followed, enables such a statement to ba accurately made, and it 
seems more just to indicate the relationship in question rather 
than to leave it to guess-work. At the risk, therefore, of making 
a somewhat wide departure from past practice, but in the 
interest of a more intelligent use of the prize system, it may 
be said that the mill which took the second prize proved to 
be 8 per cent, less meritorious than the first prize machine ; 
while the Barford & Perkins mill, which stood third in order 
of merit, was 1H per cent, inferior to the winner. 
The trials took place on June 21 and 23, in a large and 
convenient shed, whose one open side gave upon a railroad, 
extending the whole length of the shed itself, and serving to 
carry a timber stage, upon which were mounted the steam- 
engine furnishing motive power, together with an attached 
registering dynamometer, through which such motive power 
was delivered to the mills. The stage itself could be quickly 
moved, by means of a windlass and rope, from mill to mill, and 
since each exhibitor had been informed beforehand of the speed 
of the driving strap, he was already provided with a pulley of 
the proper diameter to give him such a number of revolutions 
per minute as he required. This arrangement worked very well. 
The shift from mill to mill was made in a few minutes and 
