ceeding by 1,200 pounds the provisional limit of pressure.

At the fifth round the breech block opened with some difficulty, and
an examination showed that the resistance resulted from the diametral
enlargement of the rear plate. Directions have been given to correct
this defect. The star gauge records show that no material change took
place in the diameter of the chamber or the bore. From 30 inches to 54
inches (measured from base of the breech), there was a diminution in
diameter of from 0.001 in. to 0.002 in.; in rear of 30 inches there
was no change. No enlargement in the shot chamber exceeded 0.001 in.
From the bottom of the bore (the beginning of the rifling) to the
muzzle the average enlargements were as follows: in. to 6 in., 0.005
in.; 7 in. to 14 in., 0.003 in.; 15 in. to 29 in., 0.002 in.; 30 in.
to muzzle, 0.002 to 0.001 in.

After the third round the joint between the D. and D. rings opened
slightly on the top, and measured after the 13th round showed that the
opening was about 0.004 in. wide. It cannot at present be stated
whether or not this opening increased during firing, but the defect
has been noted and will be carefully observed. Enough cocoa powder
remains to allow a comparison to be made with such brown prismatic
powder as may be adopted finally. No firing has been done as yet to
test the best position for the bands, but it will take place as soon
as enough of some standard powder is obtained to fire ten consecutive
rounds.--_Army and Navy Journal._

* * * * *

COMBUSTION, FIRE-BOXES, AND STEAM BOILERS.[1]

[Footnote 1: Address before the June Convention of the Master
Mechanics' Association.]

By JOHN A. COLEMAN.

Mr. Chairman and gentlemen: I was rash enough some time ago to promise
to prepare a paper for this occasion, the fulfillment of which prior
engagements have absolutely prevented.

I would greatly prefer to be let off altogether, but I do not like to
break down when expected to do anything; and if you have the patience
to listen for a few minutes to the reflections of an "outsider," I
will endeavor to put what I have to say in as concise form as I can,
in such manner as will do no harm, even if it does no good.

For many years I was connected with steam engineering. I was once with
the Corliss Steam Engine Company, and afterward was the agent of Mr.
Joseph Harrison, of Russian fame, for the introduction of his safety
boilers.

That br