Page:Popular Science Monthly Volume 29.djvu/193

Rh than for use. In the days when dials were used, each one contained a motto of some kind, like these: "Time flies like the shadow"; or, "I tell no hours but those that are happy."

But the dial could be used only in the daytime; and, even then, it was worthless when the sun was covered with clouds. In order to measure the hours of the night as well as the hours of the day, the Greeks and Romans used the clepsydra, which means, "The water steals away." A large jar was filled with water, and a hole was made in the bottom through which the water could run. The glass, in those days, was not transparent. No one could see from the outside how much water had escaped. So there were made, on the inside, certain marks that told the hours as the water ran out; or else a stick with notches in the edge was dipped into the water, and the depth of what was left showed the hour. Sometimes the water dropped into another jar in which a block of wood was floating, the block rising as the hours went on. Once in a while, some very rich man had a clepsydra that sounded a musical note at every hour.

Another way of measuring time among the ancients was by the sand, or hour-glass. This was made of pear-shaped bits of hollow glass with a very small opening between them. It held just sand enough to run from the upper into the lower pear in the space of one hour. The glass was then turned the other side up and the sand ran back, also taking an hour. You have seen glasses of this kind where the sand runs out in three minutes. They are used for boiling eggs. King Charlemagne, a thousand years ago, had a glass of this kind that ran for twelve hours without turning. It was marked on the outside with red lines to show the escape of the sand. Hour-glasses were so common after this that they were carried in the pocket like watches. Every minister had one to mark the length of his sermon, which was a very serious matter in England during the protectorate of Cromwell, very few sermons being as short as one hour. It is said of one minister that when the sand ran out of his glass he turned it over, saying, "I know that you are all good fellows, so let's have another glass." Once, when the preacher had turned his glass a second time, showing that he had already preached two hours, the sexton asked him to lock the door and put the key on the nail when he was through, because the few people that were left wanted to go home to dinner. We also read that, in the early history of New York, the soldiers who defended the city used hour-glasses to tell when they should go on guard.

We have seen that the dial could be used neither at night nor in cloudy weather. We have also noticed that the hour-glass had to be watched so that it might be turned at the very moment the sand ran out. And we have also seen how inconvenient it was to measure time by the running of water. None of these ways was accurate enough, for minutes and even hours would be lost. A better means of measuring time was sought for; and this was found by means of a clepsydra,