“It is in a book called ‘The Great Seal’ by a Mr. J. Cigrand,” said the boy named Billy. “I’m going to read it all when I can read a little better.” About Clocks [Illustration: EARLY AMERICAN CLOCK] “Look at my new wrist-watch! Mom gave it to me for my birthday--isn’t it a beauty?” said the boy named Billy. “Radium dial ’n all; I can see what time it is in the dark. Handy when I’m on hikes, no more stopping to scratch matches. Stem winder ’n everything.” “Goodness, Billy,” said Big Sister. “Anyone would think to hear you that there never was a watch like that of yours. We all have watches.” Billy grinned. “Well,” he said, “I’ve wanted it so long. A fellow _needs_ something to tell time by. Who discovered how to tell time anyhow?” “The first Caveman, probably,” said Somebody. “He needed to let the ladies of the family know when he was coming home to dinner, so he very likely pointed to the sun, and drew a line in the sand, to tell them that when the sunshine reached that spot he would be home and that dinner better be forthcoming pronto! That was the sundial idea, which was the only way of time-telling for ages. Cleopatra’s needle is supposed to have been one of the big sun dials. But as it was certainly inconvenient not to be able to tell the time on dark days, it was only a matter of time when some more convenient method of recording the hours would be found. When it did appear it was in the shape of the clepsydra, or water thief, a brass bowl with a hole in the bottom, which was floated on top of another bowl full of water, the principle being that when the bowl had filled itself with water an hour had passed, then a slave would empty the bowl, and hit it with a rod to announce the hour.” “But someone must have sat up all night to watch the bowl and strike the hours,” said the boy named Billy. “Precisely,” said Somebody, “so they consulted the stars, and discovered that they could divide the night into ‘watches’ of so many hours duration, and then they had different watchmen to sit up with the clepsydra, and announce the hours. “The Priests of Babylon were very wise men indeed, and it was not long until they had figured out how to divide the years into months and weeks and days and hours and minutes and seconds. “But it was not until 1581 that a young Spaniard, standing in the Cathedral of Pisa discovered, by watching a swinging lamp, the principle of the pendulum. He noticed that when it moved a short distance, it moved slowly, and that the farther it moved, the faster became the motion, making the long swing in the same time as it did the shorter one. And in this way was the pendulum applied to the making of time-telling machines. “In the 12th Century there were clocks which struck the hours, but which had no dials or hands, but after the idea of time-telling machines started it traveled fast, and in the 14th Century real clocks began to appear.