280 x .7 — 196 x 196 — 38416 X I t, = 384160.
The balance having the smaller has its mo mentum to that of the greater, as 384 is to 294. When the arcs of vibration are great, the nearer to isochronism will the long and short ones be.
When a little expence in the cylinder or horizontal 'scapement is not grudged, a ruby cylinder is certainly a great acquisition to prevent wearing on the edges; if it is not steel cased, and wholly of stone, it is so much the better, giving a little more scope to extend the limits of the banking, thc steel crank of thc other confining the extent of banking. There is no doubt a greater risk of breaking than in the cased one ; yet this might be con siderably lessened, were some attention paid to make thc notch which frees the bottom of the wheel, as has been proposed in the case of the steel cylinder, no longer than is necessary. It would be desirable to have the cylinder, formed by the strata of the sapphire or ruby, being placed in a vertical position instead of a horizontal one. This is surely attainable, when we know that diamond splitters can distinguish the strata or layers of the diamond, a stone which may be supposed more compact than either the ruby or sapphire. We have seen a cylinder, wholly of stone, in a watch belonging to a gentleman, who was wearing it when between 70 and 30 years of age ; he used frequently to let it fall without any accident happening to the cylinder. Three small griffs or cocks placed on the potence plate, so as to allow the balance edge to come into notches fitted for it, and having sufficient freedom, would prevent either the cylinder or the cock pivot from breaking. A little practice should make the stone cylin der easier, and perhaps cheaper made, than the cased one ; at all events, even on equal terms, it ought to be the preferable of the two. From what has already been said, it appears that the weight and diameter of the balance are matters not merely arbitrary ; for if the mo tive force is too great for that of the force of the balance, the watch will go fast when in the laying or horizontal position, and slow when in the vertical or hanging posi tion : by diminishing either the motive force, or making the balance heavier, the watch may be made to go the same in both positions. The properties of the pendu lum spring may conduce a little to this. It is in some degree a desideratum for a pocket watch to have the balance pivots and holes made so that the balance with its spring, when in a state by itself, and free of any com munication with the wheels, should vibrate the same length of time, whether it is in a vertical or a horizontal position. We know when it is in the last, that it will continue to vibrate twice the length of time that it will do in the other. We are humbly of opinion that this could be come at. But who will be at the trouble and expence to make such experiments as may lead to it ? Mr Earnshaw's pivots, with flat ends and shallow holes, should come very near to this object. About forty years
ago we used to hollow out the ends of balance pivots.
Lt the interim, between Tompion's having left off his trials in attempting the horizontal 'scapement, and Gra ham's having brought it to a state of perfection, M. Facio, a native of Geneva, having discovered the art of piercing holes in rubies, or any hard precious stone, came to Paris with this art as a secret ; and not being well received either by the Duke of Orleans, at that time regent of France, or by the watchmakers, lie repaired to London with it about the year 1700, which was at that time a school where the art of horology was more cultivated than at Paris. He was admitted a member of the Royal Society, and having en tered into a kind of partnership with a native of France, who had been settled in London, whose name was Debau fre, they carried on the business of Nvatc j ewe 1 Facio's partner had, at this time, contrived a new 'scape ment; it was a dead beat one, which was the thing now sought for. Plate CCCII. Fig. 4. The balance and balance wheel holes of it were jewelled ; the pallet was made of dia mond, formed from a very short cylinder of two-tenths of an inch in diameter ; the tipper end of the cylinder was cut down nearly one-half of the diameter, and lianched to the lower end and opposite side, rounded off from the circular part of the base left at top, to the lower end of the flinch, resembling something like a cone bent over, and wanting a part of the top. Two flat balance wheels, having ratchet or crown wheel sort of teeth, were on the same arbor, the teeth of the one being opposite to the middle of the spaces of the other ; the distance between these wheels was a lit tle less than the diameter of the cylinder ; the drop of the teeth in 'scaping, falls on what was left of the upper base of the cylinder, (the lower base being taken away in forming the pallet) and near to the edge formed from the fianch; here they rested during the time of the vibration of the balance. On the return, the tooth gets on the liana, and passes over it, during which, giving impulse to the balance, and escaping at the lower end, a tooth of the other wheel drops opposite on the same base of the cylinder, and so on. A watch having this 'scapement, and bearing Dcbaufre's name, was put for trial into the hands of Sir Isaac New ton, who, in sliming it to Sully in 1704, gave a very flat tering account of its performance. It attracted Sully's no tice very much, hut thinking it by no means well executed, and not being quite satisfied with two wheels, it was thought that an improvement would be made by having one wheel only and two pallets, which was part of the scheme of the 'scapement he adopted for his marine time-keeper made in 1721. Considering the genius which Sully was al lowed to possess, this was by no means an improvement on Dcbaufre's 'scapement.