. nog ■ M 
its specific heat, allowing for the exposed side of the cylinder decreasing, is equal 
to that of 
200 (l + d) d 7T 
16 
cubic feet of steam heated one degree; but the temperature will rise to the mean 
between the condensing and boiling points, or to 
160 + 212 igQ 0 
2 
or the addition of heat will be 26 degrees. The whole quantity of heat consumed 
will therefore be 
200 x 26 (l + d) dK 
16 
This divided by the capacity of the cylinder, or gives 
50 x 26 (l + d) 
Id ’ 
the loss it would sustain in temperature, or 
r = ^, l and d being here both expressed in feet. 
When the length of the cylinder is twice its diameter, or 2 d = /, the loss becomes 
r = 1950 
d 
Now one-fifth of the whole power is lost by imperfect condensation, more 
than in engines with a separate condenser; which is equal to 
—= 225 degrees of heat; 
and by the condensation and cooling in the cylinder, we have found 
1950 
d 
Hence the total heat, over and above what is required in other engines, is equi 
valent to converting into steam 
225 + 1559 
d 
1500 
times the water necessary for the steam engine, with a condenser and steam 
pressure. 
With a cylinder T5 feet diameter, double the fuel is required, but for a 6-feet 
cylinder only one-third more than in the single engine of Watt’s construction. 
164. This enables us to illustrate the fact observed by Mr. Watt, when he