390 
PROFESSOR O. REYNOLDS AND MR. W. H. MOORBT 
twenty of these observations were made for the front and then a second series of 
twenty for the back of the brake, in which case the load on the back had to lift the 
lever from its mean position. 
On taking the difference of the means of these two series of observations, the 
friction is eliminated and the resulting moment represents the error of balance of 
the brake. 
Since in the course of a trial the lever oscillates a little from its mean position, 
the brake will, when in motion, be working against the resistance offered by the 
linkage connected with the regulating cock. When at rest, however, this resistance 
will not affect the load at all. In view of this fact, two determinations of the error 
in balance were made, the first with the brake working free of the linkage, by 
allowing the small motion to take place in the slack of the pin-joints, the second 
with the brake working against the resistance of the regulating apparatus. The 
results obtained were 
In the first case, error in balance = 45‘5 ft.-lbs. 
In the second case, error in balance = 41‘73 ,, 
A mean of these two quantities would probably be approximately correct, viz., 
43’615 ft.-lbs. 
The lead balance weight previously mentioned, and weighing 13'97 lbs., was 
substituted for one of the 25-lb. weights, on the removal from the lever of the brake 
of a rider weight and a balance weight whose combined moment (par. 40) was calcu¬ 
lated at — 44’12 ft.-lbs. 
The actual uncompensated error in the balance appears therefore to be practically 
4 ft.-lb. This is so small, and the balancing of the brake such a very difficult opera¬ 
tion to perform with any approach to accuracy, that any error there may be has been 
ignored, and the balance assumed perfect in all the calculations. 
The end of the lever has always been kept at the level of the pointer indicated 
before, and by this means all error due to the varying horizontal position of the 
centre of gravity of the brake has been avoided. 
Terminal Corrections to the Apparent Heat Generated. —(Part 1., par. 31.) 
30. In order that the work done in any trial should be exactly equivalent to the 
heat generated in the water used, it was necessary that the total heat contained in 
the brake itself should be the same at the beginning and end of the trial. 
dhis condition was rarely fulfilled, since it required that the weight of water in 
the brake, together with its temperature, should be ur altered at the close of the 
trial. 
A determination was made of the amount of water contained by the brake 
