Class Xb.]

TURRET, ELECTRICAL, AND HOUSE CLOCKS.

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introduce a new description of clock, possessing bothgreater accuracy and greater strength than usual, andoue which can he made for less money than equally largeturret-clocks, of the common construction and of goixlquality.

We have already referred to M. Wagner's (of Paris )(p. 1215), collection of turret-clocks which displays greatfertility of invention; and we have awarded him aCouncil Medal for the collection, but especially for hisclock with a continuous motion, intended for the purposeof driving equatorial telescopes, so as to keep them pointedat any given star, and for all other purposes for which acontinuous, instead of an intermittent motion is required.The mode by which this is effected is particularly inge-nious as well as simple. In this, as in several others ofM. Wagner’s clocks, there is a gravity remontoire appa-ratus, on the bevelled-wheel principle, on the arbor of thewheel below the scape-wheel. For the construction ofthese remontoires we must refer to books, as it would bedifficult to give an intelligible description of them with-out drawings; but assuming that to be understood, thearm which carries the remontoire weight is in this clockprolonged to a convenient distance, so as to cany a kindof bell hung to it by a couple of wires, and within thebell a fly is driven by a train of wheels connected withthe great wheel of the clock. Tiiis fly is so adjusted,that the velocity with which it allows the train to moveis equal to the average velocity which it would have ifconnected with the pendulum, or to the velocity of a trainwith a revolving instead of a vibrating pendulum of thesame period, if the force on the clock be too great, theremontoire arm becomes raised above its average height,and the bell rising with it lets in more of the external airupon the fly, which reduces its velocity, and vice versa.In this way, the hand, or telescope, attached to that partof the train which has the continuous motion, is alwaysmade to keep pace with the average velocity of the scape-wheel with its vibrating pendulum.

M. Wagner lias exhibited a movement of this kindapplied to a long vertical barrel for measuring the forceof gravity, as in Attwood’s machine. The barrel re-volves in a second, and by the side of it a weight descendsfreely iu a groove, with an inked brush attached to it;and as the barrel revolves, the falling brush traces a curveon the surface, which exactly indicates the space descendedin any given portion of the time which the barrel takes torevolve.

Two of M. Wagner’s turret-clocks have this samebevelled-wheel remontoire in the train, only with a pro-vision for letting it off at every half-miuute, instead of acontinuous motion; and one of them has a remontoireescapement also, but by no means incapable of tripping, ifthe force is increased.

There is another clock in the same collection which de-serves particular notice on account of there being a re-montoire in it, without any additional wheel in the train.This is managed by setting the second wheel in a swing-ing frame, having its axis in a line with the arbor of thescape-wheel, and so allowing a little play sideways to thearbor of the second wheel. In this clock, also, the palletsare set in the pendulum without any crutch, the scape-wheel being put outside the frame.

Another of M. Wagner’s clocks has an escapement witha direct recoil, as in Harrison’s once famous but long agoabandoned escapement; and in this clock, also, the palletsare set on the pendulum without a crutch. It is certainlya superior contrivance to Harrison’s; although, as in his,the recoil is necessarily very great and sudden.

All the smaller clocks in this collection have cast-ironstriking parts, though the two large ones are of brass,probably for the sake of appearance; and they all strikefrom the great wheel, like Mr. Dent’s clock; but most ofthem have two hour-hammers, striking alternately, andnone of them appear to have barrels of sufficient length,in proportion to the number of striking pins, to go a weekwithout the rope going twice over the barrel. They havealso compensated pendulums, all on the lever principle;in some cases applied to the pendulum rods, and in othersfixed to the bar at the top of the clock-frame, so as todraw up the pendulum spring through a slit in the clock.

The lever compensation seems to be the only one used inFrance , except occasionally the gridiron pendulum, withnine bars of brass and steel. In English clocks, hardlyany compensation is now used, except the mercurialcylinder in the best astronomical clocks, aud the zinc tubecompensation in clocks where the mercurial pendulumwould be too expensive.

We have given a Prize Medal to M. Goirdin (p. 120-1 \a maker of some celebrity in France , for a small well-executed turret-clock, with a train remontoire of a diffe-rent construction from any of M. Wagner’s, the remontoirewheels being employed in changing velocity, or as partof the clock train, and not merely in changing direction,which is the case in the bevelled-wheel remontoire.

There are also some small turret-clocks, both byM. Chavis (p. 1200) and by M. Raima* Comte (p.1197), which we mention on account of their extraor-dinary cheapness.

Electrical clocks may be considered as connected withturret-clocks, especially in this Exhibition, in which theexperiment has been made of working three large dialsby electricity, not merely as a means of connectionwith one large clock driven by a weight in the usualway, but using electricity as the motive power. It isneedless to inform any one who has frequented theExhibition, how far that experiment has been successful;but whenever the practical difficulty is overcome, ofobtaining unfavourable electrical action, i. e of securingperfect contact of the wires at every proper epoch, thereis no doubt that some kind of remontoire action will bethe proper way of maintaining the motion of the pen-dulum, as has been attempted by Mr. Shepherd *pp. 419,422) in these clocks, and by several other exhibitors.The other plan, of making the pendulum drive the train,cannot possibly avoid such variations of force as will befatal to the isoehronism of any clock pendulum.

There is no instance in the Exhibition of a largeweight-clock driving dials at a distance by electricalconnection, either galvanic or magnetic; although thereis not found to be any difficulty in doing it by the lattermethod, by a strong permanent magnet, such as in Hen-ley’s magnetic telegraph, set on an axis, so that it canbe twisted out of contact with the armature by the forceof the great clock, whenever the remontoire is let off.The wires are coiled round the armature, in the well-known manner which is employed in telegraphs of thiskind; and they make and unmake the temporary mag-nets placed behind every dial, of which the hands are tobe kept in motion with those of the great clock by meansof ratchet-work, or pallets, worked by the alternations ofthe temporary magnets, just as in the two electrical dialsin front of the South and West Galleries.

House Clocks.

In what are called by the French civil clocks, or clocksfor domestic use, there is not much room for difference,except in the merely ornamental parts, which we havenothing to do with. There are many such clocks, ofvarious shapes, in the English part of the Exhibition, aswell as the foreign, and most of them sufficiently goodfor their purpose. Rut it is impossible to distinguish anyof the English ones as manifesting such superiority overthe rest as would justify us in giving Medals for them,because such Medals could only mislead the public intothe belief that there are not many other makers fromwhom equally good house clocks may be obtained: in-deed, some of the best makers have not thought it worthwhile to exhibit any.

Among the French exhibitors, however, we have givena Prize Medal to Messrs. Detotxhe and Houdin (p.1253), who exhibit a very handsome collection of well-made clocks, of various sizes, some with compensatedpendulums and uncommon escapements, and with whatis called equation work , or a hand to show solar as well asmean time. They also exhibit some of their pinionsseparately, which are very well made. Altogether, theircollection is well worthy of notice.

We have also given a Prize Medal lor small clocks toM. Brocot (p. 1199), the originator of an elegant andpopular form of a nearly dead escapement in ornamental

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