re as before,
and cutting off at I/2, you have an average pressure on piston head of
84 pounds, a loss of 50 per cent in economy and a gain of 42 per cent in
power. Cutting of at 3/4 gives you an average pressure of 96 pounds
throughout the stroke. A loss on cutting off at I/4 of 75 per cent in
economy, and a gain of nearly 63 per cent in power. This shows that the
most available point at which to work steam expansively is at I/4, as
the percentage of increase of power does not equal the percentage of
loss in economy. The nearer you bring the reverse lever to center of
quadrant, the earlier will the valve cut the steam and the less will be
the average pressure, while the farther away from the center the later
in the stroke will the valve cut the steam, and the greater the average
pressure, and, consequently, the greater the power. We have seen
engineers drop the reverse back in the last notch in order to make a
hard pull, and were unable to tell why they did so.

Now, as far as doing the work is concerned, it is not absolutely
necessary that you know this; but if you do know it, you are more likely
to profit by it and thereby get the best results out of your engine.
And as this is our object, we want you to know it, and be benefitted by
the knowledge. Suppose you are on the road with your engine and load,
and you have a stretch of nice road. You are carrying a good head of
steam and running with lever back in the corner or lower notch. Now
your engine will travel along its regular speed, and say you run a mile
this way and fire twice in making it. You now ought to be able to turn
around and go back on the same road with one fire by simply hooking the
lever up as short as it will allow to do the work. Your engine will
make the same time with half the fuel and water, simply because you
utilize the expansive force of the steam instead of using the live steam
from boiler. A great many good engines are condemned and said to use
too much fuel, and all because the engineer takes no pains to utilize
the steam to the best advantage.

I have already advised you to carry a "high pressure;" by a high
pressure I mean any where from I00 to I25 lbs. I have done this
expecting you to use the steam expansively whenever possible, and the
expansive force of steam increases very rapidly after you have reached
70 lbs. Steam at 80 lbs. used expansively will do nine times the work
of steam at 25 lbs. Note the difference. Press