Scientifie American: ing directly over the median line between the two spindles, I send you herewith a sketchof a scientific toy, which I the two belts were practically of equal length. Thespindles In surveying, it is often necessary to ascertain the width of have recently constructed and placed on… … having seen an engraving of what is called an electrical ing observation would prcbably never have taken place. wheel, I constructed one as shown herewith, but without the In the engraving, 1, 2, is the countershaft with its pulleys, coils. Aisa vial, about 6 inches in length by 1} inches in aandb;…
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