CLOCK. 



face of the lower great-wheel ; the 

 seconds on that of the upper or swing- 

 wheel ; and the minutes were shown in 

 a fixed dial, outside all, through holes 

 cut, in which certain small portions of 

 the other two moveable dials were ex- 

 hibited; the minute hand was attached 

 to the axle of the second great wheel, 

 which contained 120 teeth, as well as the 

 first great wheel ; the swing wheel had 

 90 teeth, the axis of the second great 

 wheel carries a pinion of 10 leaves, and 

 that of the swing wheel a pinion of 6 

 leaves. But this clock had several im- 

 perfections, from which Dr. Franklin's 

 clock is free. The smallness of the teeth 

 of the swing wheel caused the pendulum 

 to describe smaller arcs than it should 

 do; the weight of the flattering, on 

 which the seconds were engraved, load- 

 ed the axis of the swing wheel, so as 

 to cause much friction in this part, 

 which should be as free from it as 

 possible, and there was a considerable 

 difficulty in adjusting the hour plate 

 so as to correspond with the minute 

 hand. 



Another very ingenious contrivance for 

 the same purpose has been made in a 

 clock, on Dr. Franklin's principle, in the 

 possession of Mr. Patoureaux, clock- 

 maker, Wardour-street, to which the 

 tubular pendulum, on Chandler's plan, 

 before mentioned, is annexed. To the 

 axis of the great wheel of this clock 

 two concentric plates are annexed, the 

 external one of which has a groove cut 

 through it, along the line of a volute of 

 four revolutions. This groove forms a 

 trough, in which a metal ball is placed, 

 part of which is seen through its ex- 

 cavations. As the plate and groove turn 

 round, the ball rolls along the volute, 

 still approaching nearer the centre as it 

 proceeds ; and when at last it arrives 

 at the centre, it falls into another trough, 

 by which it is again conveyed to the ex- 

 ternal part of the volute; the hours are 

 engraved between the revolutions of the 

 volute, and the minutes are marked on 

 an external fixed circle, to which an in- 

 dex, annexed to the volute plate, points. 

 We have not been able to discover who 

 is the author of this ingenious invention. 

 Jt is certainly a superior method to Fer- 

 guson's ; the moveable dial being in it 

 annexed to the axle of least motion, 

 where of course its weight is of least con- 

 sequence ; and the adjustment for the 

 hours and minutes being performed in it 

 at the same time. This clock is formed 



VOT.. in. 



with a dead beat escapement, and is in- 

 tended for a regulator. 



The description of the parts of an 

 eight day clock, moved by weights, in- 

 serted a little farther on, with refer- 

 ence to the annexed plate, may serve, 

 with a little addition; to give an idea 

 of the mechanism of a clock moved by 

 a main spring. 



The spring, by which a clock is moved, 

 consists of along flat plate of steel coiled 

 up in a spiral form ; it is inclosed in a 

 cylindrical box, to which its external ex- 

 tremity is attached, while its internal end 

 is connected to a fixed axis, round 

 which the spring-box revolves. As the 

 strength of the spring is greater the 

 more it is coiled up by the turning round 

 the box, its action would be unequal in 

 impelling the work of the clock ; and to 

 remedy this inconvenience the fusee 

 wheel has been contrived. The fusee 

 consists of a conical barrel, round which 

 an heliacal groove is cut, that receives a 

 chain or catgut, previously wound round 

 the spring box, by which, as it is turned 

 round, it coils up the spring ; the groove 

 receives the chain first near the base of 

 the cone, and, as the barrel revolves, 

 gradually brings it nearer the axis ; by 

 this means, the stronger the spring is 

 coiled up, the shorter is the lever by 

 which it acts on the work; and as it 

 gradually uncoils and becomes weaker, 

 on the contrary, 1 the lever of action be- 

 comes longer. 



If instead of the barrel, in figure 2, 

 on which the catgut from the weight is 

 coiled, the fusee wheel described be 

 supposed to be substituted, and the 

 spiral spring, and its barrel and chain, 

 to be added, a good idea will be ob- 

 tained of a spring-clock ; as all the rest 

 of the work may be the same as in the 

 figure. 



Spring-clocks are generally used in 

 chambers, in places where weight-moved 

 clocks would take up too much room. 

 They are often so constructed, that their 

 frames do not hide any part of the 

 work, and are then inclosed with glass 

 covers, so that all their movements may 

 be seen ; as they are designed for orna- 

 ment as well as use, very elegant and 

 expensive decorations are frequently 

 added to them. 



The invention of moving time-pieces 

 by springs first gave rise to portable 

 time-pieces, or watches, for which see 

 the articles CHRONOMETER and HORO- 

 LOGY. 



Spring clocks are sometimes called 

 He 



