It would be superfluous to give any detailed description of the many valuable advantages derived from the science of horology, to which indeed all arts, sciences, trades, and callings are considerably indebted, and will probably be still more so in proportion to the increase of the use of steam-power and electricity. As by means of these recently-discovered powers mankind are enabled to compress into a day what would previously have required weeks and even months to accomplish, so must they regard with higher esteem, as these improvements are extended, the science by means of which they may divide and subdivide the precious minutes which are sufficient to perform so much. It will be worth while by way of illustration to point to the assistance given by horology to astronomical and nautical science. It is by means of carefully-made and exact chronometers that we calculate the distance and relations of the various heavenly bodies to ourselves and to one another. Having ascertained, by comparison, the rapidity of light and sound, and that the former travels at the rate of 192,000 miles per second, we discover that the light of the sun requires eight minutes to reach the earth, and thus compute the sun's actual distance from us. So also observing the number of seconds which elapse between the flash of lightning and the roll of thunder, or between the flash and report of a cannon, and remembering that in mild weather sound travels at the rate of 1123 feet, and in frosty weather 1080 feet in a second, we shall be able, on making allowances for the state of the atmosphere, to arrive at a tolerably correct conclusion as to distances. It is by means of a chronometer, though it be but a sand-glass, that the sailor uses his log-line at sea and finds the rate of his vessel's speed. His lead, enclosed in the log, or wood, is attached to the log-line, which has certain lengths called knots marked upon it for nautical miles, and according to the knots paid out in the half-minute of the sand-glass, so is the ship's rate of sailing, _i. e._, if ten knots are passed in half a minute the vessel's speed is at the rate of ten miles an hour. It would be both impossible and unnecessary to describe the various experiments in which it is of great consequence to measure time into minute proportions,--the number of these increases with advancing science; it will suffice if we have made the subject sufficiently interesting to the general reader to induce him to inquire further into the details. It is only by such investigations that he will be enabled to give anything like a proper answer to the question 'What is Time?' MODERN WATCHES: THEIR VARIETIES AND MODES OF MANUFACTURE. 'He that would wear a watch two things must do,-- Pocket his watch and watch his pocket too.'--_Old Maxim._