k (t'-t)dS
dR = ( -- ) ----------. (2)
60 33,000


To the same scale as the power gains, upon each ordinate, set off the
appropriate power loss, as calculated by this equation (2).

There will result the curve r, r, r, which determines the power which at
any point in the diagram is to be regarded as a loss, to be carried to
the debit side of the account. This curve of losses intersects the curve
of gains at a point (it is evident) where each equals the other.

Therefore this is the point at which expansion should cease, and this
absolute pressure is the economic terminal pressure, which determines the
number of expansions profitable under the given conditions.

In the foregoing example are taken k = 0.3070554, t' = 331.169, t = 60,
while the back pressure was taken at 7 pounds.

By way of further illustration, first let the back pressure be changed
from 7 to 5.

By equation 1 there will result a new curve of gains, W, W, W, a portion
only being plotted.

Second, let t' = 331.169 as before.
t = 150 instead of 60.
k = 0.2507097 instead of 0.3070554.