ox TPTK PrECHAXTCAL EQUTTALEXT OE HEAT. 
303 
to science that might follow from further confusion owing to error m what, in spite 
of opportunities, must be the extremely difficult task of making such complex 
determinations within less than the thousandth part. These considerations, together 
with my inability to find the large amount of time necessary for making the obser¬ 
vations, i3revented any attempt until July, 1894. At that time Mr. W.'h. Moorby 
offered to devote his time to the research, and so relieve me of all responsibility 
except that which attached to the method and the appliances ; and having, from 
experience, the highest opinion of Mr. Moorby’s qualifications for carrying out the 
very arduous research, there seemed to be no further excuse for delay, particularly 
as alter seeing the appliances in the laboratory both Lord Kelvix and Dr. Schuster 
expressed strongly their opinions as to the value of the research. 
The Oirportvnity for the Research. 
3. This consrsted in the inclusion in the original equipment, in 1888, of the labora¬ 
tory of the following appliances :— 
(1.) A set of special vertical triple-expansion steam-engines, with .separate boiler, 
closed stoke-hold, and forced blast ; these engines being specially arranged to give 
leacly acces.s to the .shafts (3 feet) above the floor, and being capable of running at 
any speeds up to 400 revolutions per minute, and working up to 100 H.P. (Plate 3.) 
(2.) Three special hydraulic brake dynamometers, on separate shafts, between and 
m line with the engine shafts, with faced couplings, so that one brake shaft could be 
coupled with the shaft of each engine, leaving each engine to work its own shaft ; or 
the brakes on the high-pressure and intermediate engines could be removed, and 
their shafts coupled by means of intermediate shafts, so that all three engines worked 
on the brake connected with the low'-pressure engine. These brakes, which are 
.shown (Plate 3), are separately capable of absorbing any power up to a maximum of 
30 horse-power at 100 revolutions, and increasing as the cube of the speed ; so that a 
single biake is capable of absorbing the whole poAver of the engine at any speed aboA^e 
100 reAmlutions a minute. 
The Avhole of the AAnrk is absorbed by the agitation of the water contained in the brake, 
while the heat so generated is discharged by a stream of water through the brake, with 
no other functions than of affording the meansof regulating,independently, the tempera¬ 
ture of the brake and the quantity of Avater in the brake. The moment of resistance 
of the brake at any speed is a definite function of the quantity of water in the brake. 
And as, except for this moment, the unloaded brake is balanced on the shaft, the 
load being suspended from a leA^er on the brake at 4 feet from the axis of the shaft, 
if the moment of resistance of the brake exceeds the moment of the load, the lever 
rises, and vice versa. By making the lever actuate the A'alve which regulates the 
discharge from the brake, and thus regulate the effluent stream, the quantity of Avater 
m the brake is continually regulated to that Avhich is just sufficient to suspend the 
