. Transactions of the American Philosophical Society. with glass handles, to bein contact with the insulated forceps F, and then approximating theother knob to the prime conductor B, the charge of the battery willpass through the wire W, as it cannot descend by the glass column,nor reach the operator through the glass handles. These should belonger than represented in the cut. LONG ZIGZAG OR ERRATIC SPARK, CONTRASTED WITH THE SHORT STRAIGHT SPARK. The cause of this difference between the lengths of the two electricities, we have nomeans of explaining.—Tliompsoris work on Heat and Electricity.
. Transactions of the American Philosophical Society. with glass handles, to bein contact with the insulated forceps F, and then approximating theother knob to the prime conductor B, the charge of the battery willpass through the wire W, as it cannot descend by the glass column,nor reach the operator through the glass handles. These should belonger than represented in the cut. LONG ZIGZAG OR ERRATIC SPARK, CONTRASTED WITH THE SHORT STRAIGHT SPARK. The cause of this difference between the lengths of the two electricities, we have nomeans of explaining.—Tliompsoris work on Heat and Electricity. The object of the engraving on the following page is to representthe different forms and lengths of the electric spark, which take placebetween a large and a small ball, accordingly as they are made nega-tive or positive. The long and zigzag, or erratic spark A takes placebetween a small ball attached to the positive pole, and a large oneassociated with the negative pole. The short straight spark B is eli- 368 DESCRIPTION OF AN ELECTRICAL MACHINE. cited under circumstances the reverse of those just mentioned. Theyare represented as simultaneous, but, with the same machine, can ofcourse, only be obtained in succession. In no respect do the phenomena of mechanical electricity appearmore favourable to the Franklinian theory, and more inexplicable,according to the doctrine of two fluids, than in the diversity of theelectrical spark in passing between a small and a large metallic ball,according to the manner in which the balls are associated with thepositive or negative poles of the machine. When the small ball isattached to the positive pole, the spark is long, comparatively narrow,and of a zigzag shape, such as lightning is often seen to assume : butwhen the situation of the balls is reversed, the spark is straight andthick, not one-third as long, and nothing of a zigzag shape can be ob-served in it. According to the Franklinian theory, when any body is more highly AND BATTERY D
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