balls in air

Over this range of spark length we shall not generally be wrong in reckoning the voltage required to produce a spark between metal balls in air at the ordinary pressure to be given by the rule: If, however, the air pressure is increased above the normal by including the spark balls in a vessel in which air can be compressed, then the spark length, corresponding to a given potential difference, very rapidly decreases.

In fact, it requires about double the voltage to force a spark of the same length through air compressed at 50lb. on the square inch that it does to make a spark of identical length between the same balls in air at normal pressure.

"And what was that?" asked the young cacique carelessly, as he tossed the golden balls in air and caught them dexterously.

Another cause of difference in the ratios is, no doubt, the relative sizes of the discharge balls in air; in the former case they were of very different size, here they were alike.

Men were not so afraid of one another; the sharp religious divisions of Oxford were absent; ideas were thrown up like balls in air, sure that some light hand would catch and pass them on.