678 Memorandum on the Xeiccastle Enr/ine Trials. 
made no attempt to repeat the trials. I have, however, satisfied 
myself by experiment that when the lubrication is constant, the 
pull on the upper ends of the levers always bears a constant 
ratio to the load on the brake. 
The amount of error due to the Appold arrangement is, I 
believe, not great for moderate powers, and Messrs. McLaren 
have given me the means of verifying this opinion. Feeling 
dissatisfied with the results obtained at Newcastle, they re- 
quested Mr. Halpin and Professor Barr to repeat the trials with 
theu" compound engine, and for this purpose they used two 
brakes, one designed by Mr. Halpin, and the other constructed 
on the same principle as those used by the Society. Messrs. 
Halpin and Barr's report was published in the Engineer of 
December 2, 1887, and indicates that considerable pains were 
taken to make the trials as accurate as possible. 
The following table gives the results obtained by Messrs. 
McLaren, and at the Newcastle trials of the Society : — 
Messrs. ilcLaren's Trial 
R. A. S. E. 
Halpin' s 
Srake 
Brake 
made like 
K. A. S. £. 
Trial 
23-7 
22-2 
24 02 
20-2 
19-1 
20-77 
211 
214 
2 267 
Water supplied per Brake H.-P. per hour . . 
22-1 
22 
21-53 
•85 
•86 
•86 
It will be seen that the figui-es agree very closely : hence we 
are bound to assuuie that the experiments at Newcastle were 
substantially accurate, or that Messrs. Halpin and Barr have 
erred to the same extent as we are supposed to have done. 
Nevertheless, as there is an undoubted source of error in the 
Society's brakes, I i-ecommend that in future trials the Appold 
levers be dispensed with, or some other form of measuring in- 
strument be adopted. Improvements in instruments devised for 
measuring power are going on constantly, and it would there- 
fore be unwise to fix on any particular form till the necessity 
for making a selection arises. 
