CLASS X.-PHILOSOPHICAL, MUSICAL, HOROLOGICAL, AND SITUATION OF CLASS 10.-It occupies the Western End of the Galleries. From L. M. 2 to 8 in the Central South Gallery; from M. 2, 3 to F. 2, 3, at the Western End, in front of the Large Organ ; from I. J. 2 to 18, in Central North Gallery, and from F. 15 to 21, in the North Gallery. Position of Groups.-Numbers referring to Pillars.-Clocks and Watches will be found in the Central South Gallery, M. 2 to 8.Globes, Orreries, &c., North-West Gallery, 1, 2, 3.-Optical Instruments, Central North Gallery, I. J. 3, 6.-Photographs, including Daguerreotypes, Talbotypes, &c. I. J. 6, 9.-Electric Telegraphs, I. J. 9, 14.-Chemical Apparatus, I. J. 14, 17.— Musical Instruments, 12 to 19.-Surgical Instruments, F. 15, 21. CLOCKS, WATCHES, &c.-Turret Clocks. (Exhibitors 55' 92, 130, 129, 679.)-The invention of clocks with wheels is ascribed to Pacificus, Archdeacon of Verona, in the ninth century, previously to which, water-clocks, and such-like EAST. 21 contrivances were employed to measure time. epitaph on Pacificus is curious :— Horologium nocturnum nullus ante viderat. En invenit argumentum et primus fundaverat ; The Clocks appear to have been set up in churches towards the end of the twelfth century; and there is a story of a clock being erected in Westminster Hall in 1298, out of a fine levied on a Lord Chief Justice; and near the same time a clock is said to have been put up in Canterbury Cathedral, and another in Wells Cathedral. From these and other notices, it seems pretty clear, that the earliest clock of which the actual construction happens to have been preserved was that made for Charles V., surnamed the "Wise," in 1379, by Henry de Wyck, who was invited by that monarch from Germany, because there was no artist in Paris of the kind-and to whom he allowed a salary of six sols a day, and free lodgings in the Tower. Clock-making was long neglected in this country. The most striking instance of neglect of horological principles was the practice of putting fans or wings to the pendulum for the supposed purpose of preventing it from occasionally swinging so far as to drive the pallets into the escape-wheel, under the influence of such a weight as was found necessary to carry the train through all the occasional impediments arising from bad cutting of the wheels, dirt, the force of the wind upon the hands, and all kinds of mechanical defects. It is a fact that, until lately, the French have been much in advance of us in this largest kind of horological engineering, and have spent much larger sums upon their public clocks, than have been expended in England. There are no less than four in Paris, which appear each to have cost about 1,000l., exclusive of some other expensive appendages, such as enamelled dials and the bells. There is not a clock in England which has cost anything near that sum. The estimates for the great clock for the New Palace at Westminster exceeds that amount; but that is to be a perfectly unique specimen. Of late, an improved style of turret-clock manufacture has been introduced by some of the best makers, and since the erection of the clock at the Royal Exchange by Mr. Dent, which contains several contrivances never before used, many have turned their attention to the improvement of turret clocks. The present Astronomer Royal, Professor Airy, has said, that he has no doubt that the Exchange clock is "the best public clock in the world," and that he believes it is superior to most astronomical clocks in the steadiness of its rate. A clock consists of a train of wheels, generally four, of which the lowest, if it is an eight-day clock, turns round in about twelve hours, or requires fourteen turns to wind it up for the week, and the highest turns in a minute. The two intermediate wheels are merely required to carry off the difference of velocity between the two extreme ones, and to work the hands. The lower of these two intermediate wheels is usually made to turn once in an hour, so that the long or minute hand may be set upon its axis or arbor, and the second wheel has nothing to do but to reduce the multiplier of sixty, or the ratio of the velocity of the highest to that of the centre wheel, as the one which carries the long hand is usually called. Among the turret clocks exhibited is an eight-day quarter turret clock (55), with compensated pendulum 8 feet long, and weighing about 2 cwt., vibrating half seconds, with pin wheel and dead escapements, but with a small recoil. All the wheels in the clock are of cast iron, except the 'scape-wheel, which is brass, of only 4 inches diameter, containing 40 pins, and turning in two minutes. The 'scape-wheel is driven by a small spiral spring fixed to a pinion which turns on a stud, set in the same line as a 'scape-wheel arbor, and carrying one of the pivot wheels of that arbor. This spring is wound up a quarter of a |