If we pass from Greece to Rome, our usual route when we are tracing a feature of our civilization, we find that the Romans were slow to introduce new methods of timekeeping. The first public sun-dial in Rome was constructed about 200 B. C., an event which the poet Plautus bewailed: Confound the man who first found out How to distinguish hours! Confound them, too Who in this place set up a sun-dial To cut and hack my days so wretchedly Into small portions! When I was a boy My stomach was my sun-dial, one more sure, Truer, and more exact than any of them, This dial told me when 'twas the proper time To go to dinner. The water-clock was brought into Rome a little later than the sun-dial, and was used as a time-check upon speakers in the law courts, just as it had been in Athens. When the Romans first began to use the clepsydra it was already a very good clock. Whether it received any great improvements at their hands is not certain. Improvements must have been made somewhere, for early in the Middle Ages we find clepsydras in forms more highly developed than they were in ancient times. In the ninth century the Emperor Charlemagne received as gift from the King of Persia a most interesting timepiece which was worked by water. "The dial was composed of twelve small doors which represented the divisions of the hours; each door opened at the hour it was intended to represent, and out of it came the same number of little balls, which fell, one by one at equal distances of time, on a brass drum. It might be told by the eye what hour it was by the number of doors that were open; and by the ear by the number of balls that fell. When it was twelve o'clock, twelve horsemen in miniature issued forth at the same time, and, marching round the dial, shut all the doors." Less wonderful than the clock of the emperor, but more useful as an object of study, is the medieval clepsydra shown in Figure 7. This looks more than ever like the clock we are accustomed to see. It has weights as well as wheels. As the float _A_ rises with the water it allows the weight _C_ to descend and turns the spindle _B_ on the end of which is the hand which marks the hours. Notice carefully that this is partly a water-clock and partly a _weight_-clock. The weight in its descent turns the spindle; the water regulates the rate at which the weight may descend. [Illustration: FIG. 7.--A MEDIEVAL CLEPSYDRA.] [Illustration: FIG. 8.--DE VICK'S CLOCK. THE FIRST WEIGHT CLOCK. (1370.)]