According to the description given by Athena (Athenæus?), the water-clock was formed of an earthenware or metal vessel filled with water, and then suspended over a reservoir whereon lines were marked indicating the hours, as the water which escaped drop by drop from the upper vessel came to the level. We find this instrument employed by most ancient nations, and in many countries it remained in use until the tenth century of the Christian era.
Fig. 143.—The Clockmaker. Designed and Engraved by J. Amman.
In one of his dialogues Plato declares that the philosophers are far more fortunate than the orators—“these being the slaves of a miserable water-clock; whereas the others are at liberty to make their discourse as long as they please.” To explain this passage, we must remember that it was the practice in the Athenian courts of justice, as subsequently in those of Rome, to measure the time allowed to the advocates for pleading by means of a water-clock. Three equal portions of water were put into it—one for the prosecutor, one for the defendant, and the third for the judge. A man was charged with the special duty of giving timely notice to each of the three speakers that his portion was nearly run out. If, on some unusual occasion, the time for one or other of the parties was doubled, it was called “adding water-clock to water-clock;” and when witnesses were giving evidence, or the text of some law was being read out, the percolation of the water was stopped: this was called aquam sustinere (to retain the water).
The hour-glass, which is still in use to a considerable extent for measuring short intervals of time, had great analogy with the water-clock, but was never susceptible of such regularity. In fact, at different periods important improvements were applied to the water-clock. Vitruvius tells us that, about one hundred years before our era, Ctesibius, a mechanician of Alexandria, added several cogged-wheels to the water-clock, one of which moved a hand, showing the hour on a dial. This must have been, so far as historical documents admit of proof, the first step towards purely mechanical horology.
In order, then, to find an authentic date in the history of horology, we must go to the eighth century, when water-clocks, still further improved, were either made or imported into France; among others, one which Pope Paul I. sent to Pepin le Bref. We must, however, believe that these instruments can have attracted but little attention, or that they were speedily forgotten; for, one hundred years later, there appeared a water-clock at the court of Charlemagne, a present from the famous caliph Aroun-al-Raschid, regarded, indeed almost celebrated, as a notable event. Of this Eginhard has left us an elaborate description. It was, he says, in brass, damaskeened with gold, and marked the hours on a dial. At the end of each hour an equal number of small iron balls fell on a bell, and made it sound as many times as the hour indicated by the needle. Twelve windows immediately opened, out of which were seen to proceed the same number of horsemen armed cap-à-pie, who, after performing divers evolutions, withdrew into the interior of the mechanism, and then the windows closed.
Shortly afterwards Pacificus, Archbishop of Verona, constructed one far superior to all that had preceded it; for, besides giving the hours, it indicated the date of the month, the days of the week, the phases of the moon, &c. But still it was only an improved water-clock. Before horology could really assume an historical date, it was necessary that for motive power weights should be substituted for water, and that the escapement should be invented; yet it was only in the beginning of the tenth century that these important discoveries were made.
“In the reign of Hugh Capet,” says M. Dubois, “there lived in France a man of great talent and reputation named Gerbert. He was born in the mountains of Auvergne, and had passed his childhood in tending flocks near Aurillac. One day some monks of the order of St. Benedict met him in the fields: they conversed with him, and finding him precociously intelligent, took him into their convent of St. Gérauld. There Gerbert soon acquired a taste for monastic life. Eager for knowledge, and devoting all his spare moments to study, he became the most learned of the community. After he had taken vows, a desire to add to his scientific attainments led him to set out for Spain. During several years he assiduously frequented the universities of the Iberian peninsula. He soon found himself too learned for Spain; for, in spite of his truly sincere piety, ignorant fanatics accused him of sorcery. As that accusation might have involved him in deplorable consequences, he preferred not to await the result; and hastily quitting the town of Salamanca, which was his ordinary residence, he came to Paris, where he very soon made himself powerful friends and protectors. At length, after having successively been monk, superior of the convent of Bobbio, in Italy, Archbishop of Rheims, tutor to Robert I., King of France, and to Otho III., Emperor of Germany, who appointed him to the see of Ravenna, Gerbert rose to the pontifical throne under the name of Sylvester II.: he died in 1003. This great man did honour to his country and to his age. He was acquainted with nearly all the dead and living languages; he was a mechanician, astronomer, physician, geometrician, algebraist, &c. He introduced the Arab numerals into France. In the seclusion of his monastic cell, as in his archiepiscopal palace, his favourite relaxation was the study of mechanics. He was skilled in making sun-dials, water-clocks, hour-glasses, and hydraulic organs. It was he who first applied weight as a motive power to horology; and, in all probability, he is the inventor of that admirable mechanism called escapement—the most beautiful, as well as the most essential, of all the inventions which have been made in horology.”
This is not the place to give a description of these two mechanisms, which can hardly be explained except with the assistance of purely technical drawings, but it may be remarked that weights are still the sole motive power of large clocks, and the escapement alluded to has been alone employed throughout the world until the end of the seventeenth century. Notwithstanding the importance of these two inventions, little use was made of them during the eleventh, twelfth, and thirteenth centuries. The water-clock and hour-glass ([Fig. 144]) continued exclusively in use. Some were ornamented and engraved with much taste; and they contributed to the decoration of apartments, as at present do our bronzes and clocks more or less costly.