WATCH, is also used for a small portable movement, or machine, for the measuring of time; having its motion regulated by a spiral spring.
Watches, strictly taken, are all such movements as show the parts of time; as clocks are such as publish it, by striking on a bell, &c. But commonly the name watch is appropriated to such as are carried in the pocket; and clock to the large movements, whether they strike the hour or not. See CLOCK.
The invention of spring or pocket watches belongs to the present age. It is true, we find mention made of a watch presented to Charles V. in the history of that prince: but this, in all probability, was no more than a kind of clock to be set on a table, some resemblance whereof we have still remaining in the ancient pieces made before the year 1670. There was also a story of a watch having been discovered in Scotland belonging to King Robert Bruce; but this we believe has turned out altogether apocryphal. The glory of this very useful invention lies between Dr Hooke and M. Huygens; but to which of them it properly belongs, has been greatly disputed; the English ascribing it to the former, and the French, Dutch, &c. to the latter. Mr Derham in his Artificial Clockmaker, says roundly, that Dr Hooke was the inventor; and adds, that he contrived various ways of regulation. One way was with a load-stone: Another with a tender straight spring, one end whereof played backwards and forwards with the balance; so that the balance was to the spring as the bob to a pendulum, and the spring as the rod thereof: A third method was with two balances, of which there
were divers sorts; some having a spiral spring to the balance for a regulator, and others without. But the way that prevailed, and which continues in mode, was with one balance, and one spring running round the upper part of the verge thereof: Though this has a disadvantage, such those with two springs, &c. were free from; in that a sudden jerk, or confused shake, will alter its vibrations, and put it in an unusual hurry.
The time of these inventions was about the year 1658; as appears among other evidences, from an inscription on one of the double balance watches presented to King Charles II. viz. Rob. Hooke inven. 1658. T. Tompion fecit, 1675. The invention presently got into reputation, both at home and abroad; and two of them were sent for by the dauphin of France. Soon after this M. Huygens's watch with a spiral spring got abroad, and made a great noise in England, as if the longitude could be found by it. It is certain, however, that his invention was later than the year 1673, when his book de Horol. Oscillat. was published; wherein he has not one word of this, though he has of several other contrivances in the same way.
One of these the lord Brouncker sent for out of France, where M. Huygens had got a patent for them. This watch agreed with Dr Hooke's in the application of the spring to the balance; only M. Huygens's had a longer spiral spring, and the pulses and beats were much slower. The balance, instead of turning quite round, as Dr Hooke's, turns several rounds every vibration.
Mr Derham suggests, that he has reason to doubt M. Huygens's fancy first was set to work by some intelligence he might have of Dr Hooke's invention from Mr Oldenburgh, or some other of his correspondents in England; and this, notwithstanding Mr Oldenburgh's attempt to vindicate himself in the Philosophical Transactions, appears to be the truth. Huygens invented divers other kinds of watches, some of them without any string or chain at all; which he called, particularly, pendulum watches.
Striking Watches are such as, besides the proper watch-part for measuring of time, have a clock part for striking the hours, &c.
Repeating Watches, are such as by pulling a string, &c. repeat the hour, quarter, or minute, at any time of the day or night.—This repetition was the invention of Mr Barlow, and first put in practice by him in larger movements or clocks about the year 1676. The contrivance immediately set the other artists to work, who soon contrived divers ways of effecting the same. But its application to pocket-watches was not known before King James II.'s reign; when the ingenious inventor above mentioned, having directed Mr Thompson to make a repeating watch, was soliciting a patent for the same. The talk of a patent engaged Mr Quare to resume the thoughts of a like contrivance, which he had had in view some years before: he now effected it; and being pressed to endeavour to prevent Mr Barlow's patent, a watch of each kind was produced before the king and council; upon trial of which, the preference was given to Mr Quare's. The difference between them was, that Barlow's was made to repeat by pushing in two pieces on each side the watch-box; one of which repeated the hour, and the other the quarter: whereas Quare's was made to repeat by a pin that struck out near the pendant, which being thrust in (as now
Watch. now it is done by thrusting in the pendant itself), repeated both the hour and quarter with the same thrust.
Plate DLXXI.
Fig. 1.
Fig. 2.
Of the Mechanism of a WATCH, properly so called. Watches, as well as clocks, are composed of wheels and pinions, and a regulator to direct the quickness or slowness of the wheels, and of a spring which communicates motion to the whole machine. But the regulator and spring of a watch are vastly inferior to the weight and pendulum of a clock, neither of which can be employed in watches. In place of a pendulum, therefore, we are obliged to use a balance (fig. 1.) to regulate the motion of a watch; and a spring (fig. 2.) which serves in place of a weight, to give motion to the wheels and balance.
The wheels of a watch, like those of a clock, are placed in a frame formed of two plates and four pillars. Fig. 3. represents the inside of a watch, after the plate (fig. 4.) is taken off. A is the barrel which contains the spring (fig. 2.); the chain is rolled about the barrel, with one end of it fixed to the barrel A (fig. 5.), and the other to the fusee B.
When a watch is wound up, the chain which was upon the barrel winds about the fusee, and by this means the spring is stretched; for the interior end of the spring is fixed by a hook to the immovable axis, about which the barrel revolves; the exterior end of the spring is fixed to the inside of the barrel, which turns upon an axis. It is therefore easy to perceive how the spring extends itself, and how its elasticity forces the barrel to turn round, and consequently obliges the chain which is upon the fusee to unfold and turn the fusee; the motion of the fusee is communicated to the wheel C (fig. 5.); then, by means of the teeth, to the pinion c, which carries the wheel D; then to the piston d, which carries the wheel E; then to the pinion e, which carries the wheel F; then to the point f, upon which is the balance-wheel G, whose pivot runs in the pieces A called the potance, and B called a follower, which are fixed on the plate fig. 4. This plate, of which only a part is represented, is applied to that of fig. 3. in such a manner that the pivots of the wheels enter into holes made in the plate fig. 3. Thus the impressed force of the spring is communicated to the wheels: and the pinion f being then connected to the wheel F, obliges it to turn (fig. 5.). This wheel acts upon the palettes of the verge, 1, 2, (fig. 1.), the axis of which carries the balance HH, (fig. 1.). The pivot I, in the end of the verge, enters into the hole c in the potance A (fig. 4.). In this figure the palettes are represented; but the balance is on the other side of the plates, as may be seen in fig. 6. The pivot 3 of the balance enters into a hole of the cock BC (fig. 7.), a perspective view of which is represented in fig. 8. Thus the balance turns between the cock and the potance c (fig. 4.), as in a kind of cage. The action of the balance wheel upon the palettes 1, 2, (fig. 1.), is the same with what we have described with regard to the same wheel in the clock; i. e. in a watch, the balance-wheel obliges the balance to vibrate backwards and forwards like a pendulum. At each vibration of the balance a palette allows a tooth of the balance-wheel to escape; so that the quickness of the motion of the wheels is entirely determined by the quickness of the vibrations of the balance; and these vibrations of the balance and motion of the wheels are produced by the action of the spring.
But the quickness or slowness of the vibrations of the
Watch. balance depend not solely upon the action of the great spring, but chiefly upon the action of the spring a, b, c, called the spiral spring (fig. 9.), situated under the balance H, and represented in perspective (fig. 6.). The exterior end of the spiral is fixed to the pin a, (fig. 9.). This pin is applied near the plate in a, (fig. 6.); the interior end of the spiral is fixed by a peg to the centre of the balance. Hence if the balance is turned upon itself, the plates remaining immovable, the spring will extend itself, and make the balance perform one revolution. Now, after the spiral is thus extended, if the balance be left to itself, the elasticity of the spiral will bring back the balance, and in this manner the alternate vibrations of the balance are produced.
In fig. 5. all the wheels above described are represented in such a manner, that you may easily perceive at first sight how the motion is communicated from the barrel to the balance.
In fig. 10. are represented the wheels under the dial-plate by which the hands are moved. The pinion a is adjusted to the force of the prolonged pivot of the wheel D (fig. 5.), and is called a cannon pinion. This wheel revolves in an hour. The end of the axis of the pinion a, upon which the minute-hand is fixed, is square; the pinion (fig. 10.) is indented into the wheel b, which is carried by the pinion a. Fig. 11. is a wheel fixed upon a barrel, into the cavity of which the pinion a enters, and upon which it turns freely. This wheel revolves in 12 hours, and carries along with it the hour-hand. For a full account of the principles upon which watches and all time-keepers are constructed, we must refer our readers to a short treatise, entitled Thoughts on the Means of improving Watches, by Thomas Mudge.