vertical cross section, Fig. 11). Here the
operation of gravity obviates the necessity of a magazine spring, but
the magazine was found to be very much in the way and liable to be
injured. It has therefore been replaced by a magazine underneath the
barrel, as in the Kropatschek and other rifles.--_Engineering_.

(_To be continued_.)

* * * * *

PRESERVATIVE LIQUID.

For a few weeks' preservation of organic objects in their original form,
dimensions, and color, Prof. Grawitz recommends a mixture composed of 21/2
ounces of chloride of sodium, 23/4 drachms of saltpeter, and 1 pint of
water, to which is to be added 3 per cent. of boric acid.--_Annales des
Travaux Publics_.

* * * * *

KENT'S TORSION BALANCE.

The United States Torsion Balance Company, of New York, has recently
brought before the public a new form of balance which presents so many
ingenious and excellent features that we illustrate it below, on the
present page. The instrument in its simplest form is shown in Fig. 1. It
consists of a beam, A, which is firmly attached to a wire or band, B, at
right angles to it, and which wire is tightly stretched by any
convenient means. Then, since the wire and beam are both horizontal in
their normal position, and since the center of gravity of the beam is
immediately above or below the middle line of the wire, the torsional
resistance of the latter tends to keep the beam horizontal and to limit
its sensitiveness. When the beam is deflected out of its horizontal
position and the wire thereby twisted, the resistance to twisting
increases with the arc of rotation. To counteract this resistance and to
render the beam sensitive to a very slight excess of load at either end,
a poise, D, is attached to the beam by a standard, C, which poise
carries the center of gravity of the structure above the axis of
rotation. This high center of gravity tends to make the beam "top
heavy," or in unstable equilibrium. By properly proportioning the poise
and its distance above the wire to the resistance of the wire, the
top-heaviness may be made to exactly neutralize the torsional
resistance, and when this is done the beam is infinitely sensitive.

[Illustration: KENT'S TORSION BALANCE. Fig 1.]

The moment of the weight or its tendency to fall increases directly as
the sine of the arc of rotation, while the torsional resistance
increases as the arc, and f