Hercules, he can rend the mountains. Fleeter than Mercury, he can outstrip the light. Gentler than Zephyr, he can assume the condition of a current, and enter our very marrow without causing pain. His name is Electricity. No one knows what he is. Some philosophers have said that he is a fluid, because he flows. As well might they call him a wild horse because he bolts, or a thief because he lurks! We prefer to call him a Spark, because in that form only is he visible—at least when handled by man.
Talking of that, it was not until the last century that master minds found out how to catch and handle our Spark. In all the previous centuries he had been roaming gaily about the world in perfect freedom; sometimes gliding silently to and fro like an angel of light; sometimes leaping forth with frightful energy in the midst of raging tempest, like a destructive demon—ripping, rending, shattering all that attempted to arrest his course. Men have feared and shunned him since the beginning of time, and with good reason, for he has killed many of the human race.
But although uncaught and untamed by them, our Spark was not altogether unknown to the ancients. So far back as the year 600 before the Christian era, Thales, one of the Greek sages, discovered that he hid himself in amber, a substance which in Greek
