he box, _j'_, when the
cavity of the valve is opposite the conduit. From the conduit, _c'_,
the coke falls upon the grate.

A small sight hole covered with glass, in the cover, J, permits the
grate to be seen when the cavity of the valve is opposite _c'_.

As in gas engines, a current of water is made to flow around the
cylinder, C', in order to keep the sides from getting too hot.

In order to set the engine in motion, we begin by opening the bottom,
C, of the cylinder, C', to clean the grate. This done, we close C and
introduce lighted charcoal through the conduit, _c'_ (the valve being
open). The valve is put in place, two or three revolutions are given
to the fly wheel, and the motor starts. The feeding is afterward done
with coke.

The parts that transmit motion operate under conditions analogous to
those under which the same parts of a steam engine do. The air pump
sucks and forces nothing but cold air, and nothing but cold air passes
through the distributing slide valve. The pump and valve are therefore
rendered very durable. The piston and cylinder, at the points where
friction exists, are at a temperature of 60 or 80 degrees. These
surfaces are protected against hot gas charged with dust.

The hot gas, which escapes from the cylinder through a valve, has
previously been cooled by contact with the sides of the cylinder and
by expansion. The eduction valve just mentioned works about like that
of a steam engine, and it is only necessary to polish it now and then
in order to keep it in good condition.--_Annales Industrielles._

* * * * *

YOUR FUTURE PROBLEMS.[1]

[Footnote 1: An address to the graduating class, Stevens
Institute, Hoboken, N.J., 1887.]

By CHARLES E. EMERY.

_Mr. President and Ladies and Gentlemen:_ It has not been considered
the duty of the speaker, in addressing the graduating class, to dwell
on the triumphs of science or the advantage of a liberal education.
These subjects have already been discussed, in connection with the
regular courses of study, better, and more at length, than he could
do. We propose rather to try and prepare the minds of the graduates
for the practical problems before them.

All young men are impressed with the consciousness of higher powers as
they increase their stores of knowledge, and this feeling perhaps
reaches its maximum with those who have made a specialty of the
investigation and application of physical law