Page:Popular Science Monthly Volume 88.djvu/156

 128

A Novel Medical Battery

A COM MUX buzzer is used in place of the induction coil and con- nected with the dry cells through a mul- tiple switch. The switch is of very sim- ple construction. A piece of brass, cut in an L, with a battery binding post at one end, which serves as a pivot and ter- minal, and a knob at the other end to swing it about, compose the arm of the switch. Brass screws are best for con- tact points. The base may be made of a scrap of wood.

The L on the arm of the switch is a little less than the distance from the center of one screw to the center of the next. Therefore when the arm is moved it contacts with the approaching screw just before it leaves the receding one, and so all the way around. This eliminates the jerk when throwing an- other batterv in the circuit.

��Bafferg

���A common electric huzzer is the

only induction coil needed for this

very simple medical battery

A wire is led from the contact screw and another from one of the binding posts of the buzzer. A round carbon from a battery is fastened to each one of these wires to provide handles through which the shock is given.

The first two batteries should be rather weak, so that persons not used to electricity may stand the shock. Any number of cells may be used, and by connecting each to a screw and to one another as shown in the drawing, the shocks may be varied from a slight vi- bration to a powerful shock.

All the batteries may be put in a box with a lid and the buzzer and switch mounted on top

��Popular Science Monthly

A Combined Triangle and Protractor

THE combination of a triangle and protractor will prove a very useful addition to the implements of the draftsman. The degrees may a

easily be marked on the "V//

surface of an ordinary ' '

celluloid triangle,

as this material io' ^^

���A good protractor may be made

by marking degrees on an ordinary

celluloid draftsman's triangle

��l/^

��is readily scratched with a sharp point. On the perpendicular of the triangle a scale may be marked, this further en- hancing the value of the instrument. The degree markings may be placed in their proper positions with the aid of a protractor.

A Drawing Cutter

IMake a handle similar to the one shown. Split it with a fine-toothed saw, in the end having the 45° angle sawed ofif, to a length about ^" longer than a safety razor blade. Make the opening fine, barely wider than a razor blade.

To use the cutter, place a safety razor blade in the slot, adjust it to the desired length by pushing forward or drawing backward, then hold by a pressure of the fingers on the sides of the handle.

���A safety razor blade has many uses.

This shows how a drawing cutter can

be made out of a blade

�� �