Page:Popular Science Monthly Volume 7.djvu/417

Rh although, to the mind of every scientific physicist, such experiments are conclusive, the objection has been raised that they do not fairly determine the case for electricity of such high tension as lightning. To meet such objections, the writer of this article, many years ago, instituted the following experiments:

Take a strip of gold-leaf half an inch wide, and two or three inches long; pass through it a moderate charge from a six-jar electrical battery, and it will be entirely burned up. The circumference of the gold in this case is one inch, and this, of course, is the measure of the surface. Now, take a gold wire one-sixteenth of an inch in diameter, and pass through it the most powerful charge that can be obtained from the same battery; the wire will remain unaffected, although it presents but one-fifth the surface.

The difference between the action of static electricity and electricity in motion is very well shown by the following simple experiment: Take a large Leyden jar, one of say two gallons measurement, having the usual knob and other arrangements, as shown in the figure. In the wooden cover insert a glass tube, carrying at its upper extremity



a wire lying horizontally across it, this wire having a good-sized ball at each end, so that the discharge may take the form of a spark or an explosion, and not pass off silently. Between the horizontal wire and the knob of the jar stretch a strip of gold-leaf (B), and charge the jar in the usual manner. So long as the electricity does not flow through the gold-leaf, the latter will remain uninjured, although it is evidently charged as intensely as the machine can charge it. But, if we discharge the jar by laying one ball of the discharger on the outer