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 



