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.

There will result the second curve of losses, R, R, R, intersecting the second curve of gains at the point F, the new economic point for our new conditions.

These two examples fully illustrate the whole subject, furnishing an easy and, when carefully made, a very exact calculation and result.

The following are a few of the general conclusions to be drawn: 

1.  That radiation is a tangible and measurable cause, sufficient to account for all losses heretofore ascribed to an intangible, immeasurable, and wholly imaginary cause, viz., “internal evaporation and re-evaporation.”

2.  In order to prevent the high initial temperatures now used becoming a source of loss, it is necessary to prevent the quantity dS (t’-t) becoming great, by making dS as small as possible.  In other words, we must compound our engines.  Thus for the first time is pointed out the true reason why compound engines are economical heat engines.

3.  The foregoing reasoning being correct, it follows that steam jackets are a delusion.

4.  In order to attain economy, we must have high initial temperatures, small high pressure cylinders, low back pressures from whatsoever cause, high piston speeds, short rather than long strokes, to avoid the cooling effects of a long piston rod; but especially must we have scrupulous and perfect protection from radiation, especially about the cylinder heads, now oftentimes left bare.

* * * * *

ELECTRICITY IN WARFARE.

[Footnote:  From a recent lecture before the Franklin Institute, Philadelphia.]

By Lieut.  B.A.  FISKE, U.S.N.

Lieutenant Fiske began by paying a tribute to the remarkable pioneer efforts of Colonel Samuel Colt, who more than forty years ago blew up several old vessels, including the gunboat Boxer and the Volta, by the use of electricity.  Congress voted Colt $17,000 for continuing his experiments, which at that day seemed almost magical; and he then blew up a vessel in motion at a distance of five miles.  Lieut.  Fiske next referred briefly to the electrical torpedoes employed in the Crimean war and our civil war.