Читать книгу A History of Inventions, Discoveries, and Origins (Vol. 1&2) - Johann Beckmann - Страница 28

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We are well assured that the ancients had machines by which, through the help of water, they were able to measure time197. The invention of them is by Vitruvius198 ascribed to Ctesibius of Alexandria, who lived under Ptolemy Euergetes, or about the year 245 before the Christian æra199. They were introduced at Rome by P. Cornelius Scipio Nasica, in the year 594 after the building of the city, or about 157 years before the birth of Christ. How these water-clocks were constructed, or whether they were different from the clepsydras, I shall not inquire. If under the latter name we understand those measurers of time which were used in courts of justice, the clepsydra is a Grecian invention, first adopted at Rome under the third consulship of Pompey200. The most common kinds of these water-clocks all, however, corresponded in this, that the water issued drop by drop through a hole of the vessel, and fell into another, in which a light body that floated marked the height of the water as it rose, and, by these means, the time that had elapsed. They all had this failing in common, that the water at first flowed out rapidly, and afterwards more slowly, so that they required much care and regulation201.

That ingenious machine, which we have at present under the name of a water-clock, was invented in the seventeenth century. The precise time seems to be uncertain; but had it been before the year 1643202, Kircher, who mentions all the machines of this kind then known, would in all probability have taken notice of it. It consists of a cylinder divided into several small cells, and suspended by a thread fixed to its axis in a frame on which the hour distances, found by trial, are marked out. As the water flows from the one cell into the other, it changes very slowly the centre of gravity of the cylinder, and puts it in motion203; much like the quicksilver puppets invented by the Chinese204.

These machines must have been very scarce in France in 1691; for Graverol at that time gave a figure and description of the external parts of one, but promised to give the internal construction as soon as he should become acquainted with it205. This was the only one then in Nismes. He says, also, that they were invented a little before by an Italian Jesuit, who resided at Bologna, but were brought to perfection by Taliaisson, professor of law at Toulouse, and a young clergyman named De l’Isle.

Alexander says more than once that this machine was invented at Sens in Burgundy, in 1690, by Dom Charles Vailly, a Benedictine of the brotherhood of St. Maur, and that he brought it to perfection by the assistance of a pewterer there, named Regnard. This account is in some measure confirmed by Ozanam; for he says expressly, that the first water-clocks were brought from Burgundy to Paris in 1693, and he describes one which was made of tin at Sens. Dom Charles Vailly was born at Paris in 1646, and died in 1726; he was celebrated on account of his mathematical knowledge, though he is known by no works, as he burned all his manuscripts206.

Alexander, however, who was of the same order, seems to have ascribed to his brother Benedictine an honour to which he was not entitled; for Dominic Martinelli, an Italian of Spoletto, published at Venice, in 1663, a treatise written expressly on these water-clocks, which Ozanam got translated into French by one of his friends, and caused to be printed with his additions207. This translator says that water-clocks were known in France twenty years earlier than Ozanam had imagined. It appears therefore that they were invented in Italy about the middle of the seventeenth century, and that Vailly, perhaps, may have first made them known in France208.

It may perhaps afford some pleasure to those who are fond of the history of the arts, to know that Salmon, an ingenious pewterer at Chartres in France, has given very full and ample directions how to construct and use this machine209. He is of opinion that the invention is scarcely a century old; and that these water-clocks, which are now common, were first made for sale and brought into use among the people in the country, by a pewterer at Sens in Burgundy. What this artist affirms, that they can be constructed of no metal so easily, so accurately, and to last so long as of tin, is perfectly true. I have however in my possession one of brass, which is well constructed; but it suffers a little from acids. Among the newest improvements to this machine may be reckoned an alarum, which consists of a bell and small wheels, like those of a clock that strikes the hours, screwed to the top of the frame in which the cylinder is suspended. The axis of the cylinder, at the hour when one is desirous of being wakened, pushes down a small crank, which, by letting fall a weight, puts the alarum in motion. A dial-plate with a handle is also placed sometimes over the frame.

[A very ingenious application of the principle of the clepsydra, for the purpose of measuring accurately very small intervals of time, is due to the late Captain H. Kater. Mercury is allowed to flow from a small orifice in the bottom of a vessel, kept constantly filled to a certain height. At the moment of noting any event, the stream is interrupted and turned aside into a receiver, into which it continues to run till the moment of noting any other event, when the intercepting cause is suddenly removed. The stream then flows in its original course. The weight of mercury in the receiver, compared with the weight of that which passes through the orifice in a given time, observed by the clock, gives the interval between the events.]