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ELECTRIC ERYGMASCOPE.

The erygmascope is the name of an electric lighting apparatus designed for the examination of the strata of earth traversed by boring apparatus.

It consists of a very powerful incandescent lamp inclosed in a metallic cylinder.  One of the two semi-cylindrical sides constitutes the reflector, and the other, which is of thick glass, allows of the passage of the luminous rays, which thus illuminate with great brilliancy the strata of earth traversed by the instrument.  The base, which is inclined at an angle of 45 deg., is an elliptical mirror, and the top, of straight section, is open in order to permit the observer standing at the mouth of the well, and provided with a powerful spyglass, to see in the mirror the image of the earth.  The lamp is so mounted that its upwardly emitted rays are intercepted.

The whole apparatus is suspended from a long cable, formed of two conducting wires, which winds around a windlass with metallic journals which are electrically insulated.  These journals communicate, through the intermedium of two friction springs, with the conductors on the one hand and, on the other, with the poles of an automatic and portable battery.

[Illustration:  THE TROUVE ERYGMASCOPE.]

This permits of lowering and raising the apparatus at will, without derangement, and without its being necessary to interrupt the light and the observation.—­Revue Industrielle.

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A NEW ELECTRIC BALLISTIC TARGET.

The electrical target usually employed in determining velocities of projectiles consists of a wooden frame on which is strung a copper wire so as to make a continuous circuit arranged in parallel vertical lines about one inch or one and one half inches apart.

It frequently happens that a projectile will pass through this target without breaking the circuit, either by squeezing between the wires or because, when last repaired, the target was short-circuited unnoticed, so that the cutting of the wires did not break the circuit.  The repair of this target takes considerable time.

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