744 
ME. MACQTJOEN EAXKIISTE OX STEAM-EXODsES. 
estimated at 11,560,000 foot-pounds. Hence the efficiency of the furnace and holier was 
10,110,000 n.CQ 
11 , 560 , 000 "”^ 
In this case the short duration of the experiment on the consumption of coal, which 
was interrupted by a fog, makes the result less satisfactory than it would haye been if 
the experiment had been continued, as intended, for several hours. The engine and 
boiler were of a kind invented some years ago by Mr. Ceaddock ; the boiler consisting 
chiefly of a sort of cage of vertical water-tubes enclosing each fire-grate. The heating 
surface was about nine times as great, relatively to the fuel burned, as it is in ordinary 
marine boilers. 
Example III. — Paddle -steamer ‘ Callao,’ built by Messrs. JoHX Eeid and Co. ; the 
engines by Messrs. Kandolph, Eldee and Co. ; displacement 1100 tons ; speed vath 
1176 indicated horse-power 12-05 nautical miles per hour. 
Available heat expended per hour in foot-pounds per indicated horse-power, 
1 , 980,000 
efficiency of steam 
1^5^^=14,143,000 foot-lbs. 
n* I ^ ' 
Coal burned per indicated horse-power per hour, 2-67 lbs. 
Available heat of combustion of 1 lb. of coal, 
5,300,000 ; 
being nearly the same as in Example I. 
The boilers in this case were, like those in Case I., improved marine boilers of ordi- 
nary proportions. In such boilers, 5,400,000 foot-lbs. may be considered a fair estimate 
of the available heat of combustion of good ordinary steam-coal. 
