600 The Trials of Light Portable Motors at Plymouth. 
Explosions 
per minuta 
4 hours 28 minutes 86 
4 „ 33 „ 76 
4 „ 40 „ 92 
4 „ 50 „ 91 
5 „ 10 „ 82 
5 „ 40 I, 72 
Mean , 83 
The following is the oil account for this trial, which lasted 
90 minutes : — 
lb. 
Oil used in cylinder 475 
Oil used for igniting lamps '28 
Total . . . ' . . . . 5-03 
At the end of the trial fourteen ounces of oil were found to 
have accumulated in the vaporiser. If all this accumulated 
during the period of the trial, it should be deducted from the 
amount given above. It is more probable, however, that it 
accumulated in the vaporiser during the long and unsatisfactory 
attempt to start the engine. 
Analysis of the oil used. — An analysis of the petroleum 
oil used in the Priestman Engine trial has been made by Mr. 
Charles J. Wilson. He reports thus : — 
The sample of oil received from Prof. Unwin, June 24, 1890, and marked 
" Priestman Engine," gave the following results on examination : — 
Specific gravity at 15°-5 C. =0 8101. 
Composition hy weight : — 
Carbon 80 01 per cent. 
Hydrogen 1390 „ 
Undetermined 009 ,. 
10000 
Fractional distillation : — » 
From 160° to 205° C 18 volumes per cent. 
„ 205° to 210° 
210° to 220° 
220° to 240° 
240° to 270° 
10 
18 
28 
25 
Heating value. The composition by weight multiplied by the usual 
factors gives, 
0-8001 x 8,080 = 6949-6 
0-1390 x 29,000 =40310 
10980 6 
Henco evaporation per lb. of oil = —j^— = ^0'4 lb. 
This figure is not an accurate one, but I am not acquainted with any 
method by which the heating value of such a material can be precisely 
determined. Chahles J. Wilson. 
