Page:Popular Science Monthly Volume 88.djvu/55

Popular Science Monthly

with lenses and measuring instruments that are wonderfully accurate.

In the Marindin range finder, which is the type most commonly used in the British infantry, an optical arrangement is used, having an equivalent of two eyes mounted thirty-one and a half inches apart. Two reflecting prisms are employed, so that the rays are brought together in a combined beam to the eye of the range officer.

A more complicated form of range finder is one equipped with magnifying lenses and an adjustable prism by means of which the instrument can be used for recording distances. When the instrument is directed towards some distant object, it will be split into unmatched halves until the prism is adjusted to the correct angle. The distance is then indicated on a dial.

Range finders used on battleships are fundamentally the same as the Maradin finder. They differ only in details.

HE electromagnet has long been used by surgeons to extract splinters from the eye. It has not proved so serviceable when its use has been extended to other parts of the body. In the present war surgeons found that deeplying fragments of shrapnel are literally torn out by the magnet, with the result that gaping wounds are produced which are difficult to handle. For that reason army surgeons, in Germany at least, prefer to restrict the use of the electromagnet to those cases in which the steel splinters lie very near the surface.

NOVEL device which announces to the cbauffeur any overheating of his engine is made so that a streamer is released from the radiator cap to blow against the windshield. The ribbon is made of a bright-colored material, and shows at night as well as in the daytime.