The Trials of Oil Engines at Cambridge. 733 
The cost of this oil was 8 \d. per gallon, delivered at 
Cambridge, from which has to be deducted the value of the cask, 
which would reduce the price to about 7 d. a gallon, or nearly 
twice the price of the Russolene. Indicator cards taken upon 
this run are copied in figs. 23 and 24 (p. 731), and show that in 
the Crossley engine a much sharper and straighter explosion line 
is obtained with this oil, while the mean pressure is much lower — 
namely, 63’6 lb. per square inch. In the Hornsby engine there 
is little difference, but the initial pressure is lower than with 
Russolene. 
The engines had been previously cleaned, which would ac- 
count for their rather higher mechanical efficiency upon this trial. 
The results are given in the table on p. 732. The economy 
of the Crossley engine was still greater with this oil than with 
Russolene. 
The trial was made with a flying stai-t, and the lamp oil could 
not, therefore, be measured in the case of the Crossley engine. 
It has been allowed for at the same rate as on the full-power 
Russolene trial. This is no doubt more, rather than less, than it 
would actually use, as in that quantity will be included the 
oil burnt during the ten minutes required to start. 
An approximate heat balance would stand as follows for the 
two full-power trials for the two engines in question : — 
Full-Power Trials. 
Expenditure of Heat, B.T.U.’s per min. 
Russolene 
Broxbourne 
— 
Hornsby 
Per- 
centage 
Crossley 
Per- 
centage 
Hornsby 
Per- 
centage 
Crossley 
Per- 
centage 
Thermal value of oil \ 
used per min. . J 
B.T.U. 
2,580 
1000 
B.T.U. 
1,770 
1000 
B.T.U. 
2,930 
1000 
B.T.U. 
1,850 
1000 
Heat expended in use- 1 
ful work= B.H.P. J 
363 
14 
297 
16-7 
351 
120 
324 
17-6 
Heat lost by friction . 
74 
29 
39 
22 
67 
23 
31 
1-7 
Heat shewn on indica- ; 
tor diagram (I. H.P.) 
437 
16*9 
336 
189 
418 
143 
355 
19-2 
Heat rejected in jackets 
763 
29'5 
424 
24 
887 
303 
382 
207 
Heat rejected in ex- i 
liaust and other j, 
losses . . . j 
1,380 
53-6 
1,010 
57-1 
1,626 
55'4 
1,118 
601 
VOL. V. T. s. — 20 3 c 
