Portahte Agricultural Steam iEvgines at Neiccastte. 709 
77ie Creditor Side of the Account. 
The units of heat thus resulting from the combustion of the 
wood and of the coal we know to have been disposed of in 
the nine specified ways which follow, and even, after allowing 
for all of these, there is still some 3j per cent, for the dissipa- 
tion of which we do not pretend to account with certainty. 
No. 1. — By evaporating the water in the rekindling wood, and 
heating the steam of this water to the temperature of the smoke- 
box, at which temperature it escaped into the air. Now, as 
the wood was not dried before being used, there has to be con- 
sidered, under this head, the 3*08 lbs. of absolute wetness which 
could be got rid of by drying ; but in addition to this, we 
must take into account the inchoate water of which we have 
spoken, amounting to 10"92 lbs. x '4643, namely, the oxygen 
with its corresponding hydrogen. This comes to 5"07, which 
added to the 3'08 of wetness, gives 8*15 lbs. ,of water to be 
vaporised and heated. 
Let us see what demand this makes upon the heat units. 
The 8'15 lbs. of water would have to be heated from 70° to 
212°, would need to be evaporated at that temperature, and the 
steam formed would require to be heated from 212° to 385°. 
The rise of temperature of the steam from 212° to 385°, or 
, 173°, must be multiplied by "37, the specific heat of steam at 
constant volume, in order to get the number of units of heat 
expended in warming it. There was therefore required for this 
process 
142° + 996-6= + (173 X -37) = 1172-6 units per 1 lb. of water. 
The heat expended in this work for the whole number of 
pounds was therefore 
^ 8-15 lbs. X 1172-6 u. = 9557 units. 
H 
n No. 2. — The consumption of heat units by heating from 70° 
I to 385° the wood and the air required for its combustion. 
I It appears, from experiments that have been made by others, 
■ that 1 lb. of wood similar to that which was used, but after 
■ drying, requires 6 '084 lb. of air for its combustion. Of the 
||Iried wood we have shown that '4643 was in the form of 
Pnchoate water. There remains therefore, in each lb. of dried 
.vood only "5357 to be associated with the air, making there- 
ore, for each lb. of dried wood, 6-6197 lbs. of matter, which 
lave to be raised 315°, i.e. from 70° to 385°. 
A small portion of this matter, i.e. '0756, being the union of 
8 A 2 
