It was found by comparing the direction shown by the mariners’ compass with that found by means of the North Star, that the north pole of the compass pointed south, and the south pole north. In fact the needle had been reversed, and the ship was steered into Boston harbour with the compass reversed. Even at that time people had guessed that the lightning had something to do with electric force, a guess which Benjamin Franklin afterwards proved to be true. Robert Boyle observed that hair easily shows electric attraction. It can be “electrified,” as we say now. When a cat has been lying by the fire for some time and we stroke her with the hand, we hear a slight crackling noise as if from small sparks. Some parts of the fur stick together, others stand apart. This is also observed by ladies when they comb their hair. When the hair is very dry, individual hairs fly apart. False hair, which is usually drier than growing hair, shows electrical attraction very strikingly. Boyle observed this more than two hundred years ago. He wrote to a friend, “false locks of hair brought to a certain degree of dryness are attracted by the flesh of some persons. Of this I had proof in two beautiful ladies who wore them. For at some time I observed that they could not keep them from flying to their cheek and sticking there, though neither of them had any occasion for paint, nor used it. One of them gave me leave to make a further experiment, and asking her to hold her warm hand at a convenient distance from one of those locks taken off and suspended in free air, as soon as she did this the lower end of the lock which was free attached itself to her hand.” It was soon found that other substances besides amber and hair show electric attraction. Isaac Newton hung a round piece of glass in a brass ring fixed about an inch above a table. He rubbed the glass with some “rough and raking stuff,” till some very small fragments of very thin paper laid on the table beside the glass began to be attracted and moved nimbly to and fro, leaping upon the glass and remaining there a while, then leaping down and resting there, then leaping up and perhaps down and up again. This experiment is repeated easily by rubbing a stick of sealing wax with a woollen cloth, and holding it over small bits of paper. [Illustration: Fig. 47.--Guericke’s Electrical Machine made with a Ball of Sulphur.] Instead of rubbing amber or glass, Guericke rubbed a ball of sulphur with his hands. He made this ball by filling a round bottle with flowers of sulphur and melting the sulphur until it was quite liquid. Then he let it cool until it was solid, and then he broke the bottle and took out the sulphur ball. He attached the ball to a stick, and when he had electrified it by rubbing, he used it to attract feathers, which he succeeded in leading all round a room by this electric force only.