for this launch, we find that they are nearly equal--each approaches 50
cwt; but in the case of the steam launch we include 10 cwt. of coals,
which can be stowed into the bunkers, and which allow fifteen hours
continuous steaming, whereas the electric energy stored up will only
give us seven and a half hours with perfect safety.

I have here allowed 8 lb. of coal per indicated horse power per hour,
and 10 horse power giving off 7 mechanical horse power on the screw
shaft; this is an example of an average launch engine. There are launch
engines in existence which do not consume one-half that amount of fuel,
but these are so few, so rare, and so expensive, that I have neglected
them in this account.

Not many years ago, a steam launch carrying a seven hours supply of fuel
was considered marvelous.

Our present accumulaton supplies 33,000 foot pounds of work per pound of
lead, but theoretically one pound of lead manifests an energy equal to
360,000 foot pounds in the separation from its oxide; and in the case of
iron, Prof. Osborne Reynolds told us in this place, the energy evolved
by its oxidation is equivalent to 1,900,000 foot pounds per pound of
metal. How nearly these limits may be approached will he the problem
of the chemist; to prophesy is dangerous, while science and its
applications are advancing at this rapid rate.

Theoretically, then, with our weight of fully oxidized lead we should be
able to travel for 82 hours; with the same weight of iron for 430 hours,
or 18 days and nights continually, at the rate of 8 miles per hour, with
one change. Of course, these feats are quite impossible. We might as
well dream of getting 5 horse power out of a steam engine for one pound