tching action. The machine shown is designed to operate on sheet
iron from No. 7 to No. 30 gauge, and up to 36 in. wide, the limit for
length being 120 in. About a dozen sheets can be operated on at once.
The machine appears to have met with considerable success in America,
and has been used for mild steel, iron, galvanized or tinned sheets,
copper, brass, and zinc. The details of this machine are given in Figs.
1 to 8. Figs. 1 and 2 are a plan and side elevation of the bed of the
machine, showing the position of the hydraulic ram. Fig. 3 shows the
bars used for holding the back jaws in position, with the holes for
adjusting to different lengths of the plates. Fig. 4 is a back view and
section of the crosshead and one of the bolts that connect the moving
grip with the hydraulic ram. Fig. 5 gives a plan and cross section of
the back grip, and Fig. 6 is a back elevation of the same, with a front
view and section of the gripping part. Fig. 7 shows the gear by which
the jaws are opened and closed.

[Illustration: BRITTON'S PLATE STRAIGHTENING MACHINE.]

* * * * *

THE SCHOLAR'S COMPASSES.

Among the numerous arrangements that have been devised for drawing
circles in diagrams, sketches, etc., one of the simplest is doubtless
that which is represented in the accompanying figure, and which is known
in England as the "scholar's compasses." It consists of a socket into
which slides a pencil by hard friction, and to which is hinged a
tapering, pointed leg. This latter and the pencil are held at the proper
distance apart by means of a slotted strip of metal and a binding screw.
When the instrument is closed, as shown in the figure to the left, it
takes up but little space, and may be easily carried in the pocket
without the point tearing the clothing, as the binding screw holds the
leg firmly against the pencil.

The mode of using the apparatus is so well shown in the figure to the
right that it is unnecessary to enter into any explanation.--_La
Nature_.

[Illustration: THE SCHOLAR'S COMPASSES.]

* * * * *

THE INTEGRAPH.

In scientific researches in the domain of physics we often meet with the
following problem: Being given any function whatever, y = f(x), to find
a curve whose equation shall be

_
/
|
y = | f(x)dx + C.
|
_/

[TEX: y = \int f(x) dx + C.]

Let us take an example that touches us more closely; l