nditions.

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.

At the present day, an electrical torpedo may be described as consisting
of a strong, water-tight vessel of iron or steel, which contains a large
amount of some explosive, usually gun-cotton, and a device for detonating
this explosive by electricity. The old mechanical mine used in our civil
war did not know a friendly ship from a hostile one, and would sink
either with absolute impartiality. But the electrical submarine mine,
being exploded only when a current of electricity is sent through i