Trebel, George. [from old catalog] · New York, F. Tousey · leaf 62
iation in pres-sure is especially noticeable wnen eitner or both of the parts arecarbon. Now any slight jar, as that caused by the tick of awatch, will cause a variation in the pressure between the car-bon buttons, and this will produce a corresponding variationin the current, and the fluctuations… … 56 HOW TO MAKE AND or the footfall of an insect, may be reproduced a considerabledistance, and be as audible as though the original sounds weremade close to the ear. If a person talk to the thin pineboard, his words will be distinctly heard in the receiver. The last subject which we will consider…
Electricity
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