Page:Popular Science Monthly Volume 92.djvu/241

 Popular Science MontJily

��Which CyHiider Is Missing Fire? Find Out from the Seat

THE invention shown in the accompanying il- lustration can be used either as a test- ing apparatus for shop work or as a permanenj; device to be placed on the dash of an automo- bile. The chauffeur can determine easi- ly and quickly just which one of his engine cylinders is missing fire with- out getting out of

Wires to spark plug

���225

rally, if a particular cylinder is not firing properly, its power will not be sufficient to carry all the pistons over and against the combined com- pressions. There- fore, by allowing the current to pass through each spark plug, if necessary, the offending one caasoon be located. If the cylinder is firing, as it should, the engine will run without help from the other cylinders.

���Showing the mechanism of the ignition-detector. Us- ing it, the chauffeur can test his cyUnders with- out getting out of the car

��Mandolin Music

Via the Tuneful

Molar

T last someone

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��alindef cut switches

��his seat or raising the hood over the engine. The offending cylinder is de- tected by shutting off the ignition circuit of all the cylinders except one and allowing this one to pull the others against compression. To shut off the circuits, little contact plugs on the front of a box on the dashboard are depressed by means of small handles which force any par- ticular strip back against a bus bar at the rear. When this is done, the current is shunted from the plug through the lead and bus bar back to the current source through the usual ground wire. Natu-

���New mandolin design promises to make the human tooth famous

��ed what has ailed the mandolin these many years. With his trained archi- tectural eye and his well-developed sense of what's what in ornamental designing, R. C. Petty, of Drumright, Oklahoma, has decided that the vitals of the instru- ment are in good order but the general contour of the thing is all wrong. Ac- cordingly, he has invented an instrument which for beauty of line and lavishness of design is without a peer.

Exhibiting a marked degree of originality, he has chosen the human tooth for his model. Look at the accom- panying illustration and you will see how faithfully this knight of the strings has fol- lowed the graceful outlines of the molar. But he has taken away none of the en* trancing melodic quality of the instrument itself. In its nevvf and more beautiful shape, the mandolin may be said to be even more tuneful, if such a thing is possible.

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