Report on the Trials of Implements at Oxford. 447 
and with the requisite weight held suspended by the break. When this fair 
running condition is reached, no more coals are put upon the fire; but it is 
sutlered to barn down and the steam to lower, until the engine will no longer 
run at the proper pace, care being taken that every steam-valve or expansion- 
valve be open, so that the engine can take full advantage of the lowering 
pressure of steam in the boiler. Then, the fire being all but out, only just so 
much as will light the fresh coals, and the ashes being most carefully laked 
out of the ashpan, the exhibitor starts with a fresh supply of coals, being 
allowed 14 lbs. per nominal horse-power. With these coals he gets up steam 
to the working pressure — which this year was 50 lbs. to the square inch — and 
then he re-stokes his engine and works the break as long as he can possibly 
make his coals and ashes last. 
So soon, again, as, with every valve wide open, the engine ceases to keep its 
speed, the Judge in charge of the experiment stops the engine and then reads 
the counter attached to the break (the counter being similar in principle to that 
attached to gas-meters), and from this reading ascertains how many revolutions 
the break has made during the time the coals have been burning. This time, 
divided by the calculated number of revolutions of the break per minute, gives 
the amount of ireah-tmxQ during which the engine has been running. " Break- 
time " is used because it is iraiwssible to keep the engine running with absolute 
regularity ; and thus an engine which has been running three hours of actual 
time, if it has been making a few more revolutions than it was arranged to 
make, may have run, say three hours, ten, twenty, or thirty minutes of break- 
time. Care is taken that the water should show at the same height in the 
water-gauge of the boiler at the terminatioQ of the experiment as at its com- 
mencement ; as were this point neglected, the exhibitor might, on the one 
hand, have been getting power out of water which was heated in a previous 
experiment, or, on the other hand, he may have been heating water which 
he would never use. As the water ordinarily rises in the gauge immediately 
on starting the engine, it is well to take the height just before starting and 
just after. It is difficult to say whether it is more amusing or more provoking 
to witness, and to have to struggle with the ingenuity of some of the exhibitors' 
representatives, who do try their very hardest to make the engine stop in its 
preliminary trial with high steam, a large fire, and the valves not fully open ; 
and then at the final trial to stop with all these conditions reversed ; and the 
Judges have to be very careful indeed that the conditions at the final trial are 
precisely identical with the preliminary one. 
We believe that trials thus conducted do truly give the results obtained by 
each exhibitor for a given weight of fuel burnt, but in the class of engines with 
boilers combined, it is impossible to say, with acciu'acy, whether the merit or 
demerit of any particular engine is due to the engine, or to the boiler, or to 
both, or to a third most important element — and that is the ability of the 
stoker. But a further investigation as to the quantity of the water evaporated 
would go far to enable the J udges to solve some of these problems ; for instance, 
if one en'_;ine did half as well as another, and it were found that its boiler and 
stoker together evaporated only one half the water that the other boiler 
and stoker evaporated, it would then be clear that the engines, qua engines, were 
of equal merit, because the one that was supplied with half the steam did half 
the work done by the other that was supplied with the full volume of steam ; 
but whether the suggested difference in evaporation was due to the boiler or 
to the stoking, it would be always all but impossible to ascertain. It is true 
experiments might be made by appointing one man to fire several boilers, but 
unless that were done the Judges see no means, in this class of engines, 
beyond their ability of expressing an opinion from a priori reasoning upon the 
boilers' merits, of determining whether the power of evaporating water econo- 
mically is due to the boiler or to the stoking. But in the class of fixed engines 
