The artificial clock-maker a treatise of watch, and clock-work, wherein the art of calculating numbers for most sorts of movements is explained to the capacity of the unlearned : also, the history of clock-work, both ancient and modern, with other useful matters, never before published / by W.D.

CHAP. VIII. Of the Invention of those Pocket-Watches, commonly called Pendu∣lum Watches. (Book 8)

§ 1. THe reason they are called Pen∣dulum-Watches, is from the regularity of their Strokes, and Motion.

Which exactness is effected by the govern∣ment of a small Spiral Spring, running round the upper part of the Verge of the Ballance: which Spring is called the Regu∣lator.

§ 2. The first Inventer hereof, was ••hat ingenious and learned member of our Royal-Society, Dr Hook: who contrived va∣••ious ways of Regulation. One way was ••ith a Load-stone: another was with a ••nder strait Spring▪ one end whereof ••layed backward, and forward, with the ••allance: So that the ballance was to this ••pring as the bob of a Pendulum, and the ••ttle Spring, as the Rod thereof. And se∣••eral other contrivances he had besides of ••is nature.

§ 3. But the Invention which best an∣••ered expectation, was at first, with two ••llances: of which I have seen two sorts, ••ho there were several others. One ••ay was without Spiral Springs, the ••her with. They both agreed in this, ••hat the outward Rims of both the Bal∣••nces, had alike number of Teeth; which ••nning in each other, caused each Bal∣••nce to vibrate alike.

But as to the former of these, which had no Spiral Spring▪ the Verges of its Bal∣lances, had each but one Pallet apiece, about the middle of the Verge. The Crown-wheel lay (contrary to others) re∣versed, in the middle of the Watch, in the place, and after the manner of the Contrate-wheel. The teeth of this Crown-wheel, were cut after the manner of Con∣trate-wheel teeth, viz. lying upwards, but very wide apart, so as that the Pal∣lets (which were about one tenth of an inch long, and n••rrow) might play in and out between each tooth. The Verges of the two Ballances, were set one on one side, the other on the other side of the Crown-wheel, so that the Pallets might play freely in its teeth. And when the Crown-wheel in moving round, had de∣livered its self of one Pallet, the other Pallet on the opposite side, was drawn on to make its Beat, by means of the mo∣tion which the other Ballance had given its Ballance, (the two Ballances moving one another, as hath been said in the be∣ginning of this Paragraph.) And so the same back again.

It may be here noted, that for the more clear understanding of the last contri∣vance, I have described the two Ballances, as having Teeth on the edges of their Rims, running in one another. But the contrivance was really thus▪ There was a small Wheel under each Ballance, propor∣tioned to the width of the Crown-wheel. But the Ballances were much larger. And so the Teeth of these two little fore∣said Wheels or Ballances, running in one another, moved the larger Ballances above them, all one, as if these two great Bal∣lances had been toothed and played in each other.

§ 4. The other way, with two Bal∣lances also, moving each other (as was said in the beginning of the last §) had a Spiral Spring to each Ballance, for its Re∣gulator. In this Invention, only one Bal∣lance had the Pallets, as the common Ballances have: and the Crown-wheel operated upon it, according to the usual way. But then when this Ballance vi∣brateth, it giveth the same motion back∣ward and forward, to the other ballance; as hath been said.

The first of these two ways, was never prosecuted so far, as perhaps it deserved. And the excellency of the latter is, that no jirk, or the most confused shake, can in the least alter its Vibrations. Which it will do in the best Pendulum Watch with one ballance now commonly used. For if you lay one of these Watches upon a Table, and by the Pendant jirk it back∣ward and forward, you will put it into the greatest hurry; whereas the last menti∣oned Watch, with two ballances, will be nothing affected with it. But notwith∣standing this inconvenience, yet the Watch with one ballance and one Spring (which was also Dr. Hooks Invention) prevailed, and grew common, being now the uni∣versal Mode: but of the other very few were ever made. The reason hereof, I judge, was the great trouble and vast nice∣ness required in it, and perhaps a little foulness in the ballance-teeth may retard the motion of the ballances. But the o∣ther is easier made, and performeth well enough, and in a pocket is scarce subject to the aforesaid disorder, which is caused rather by a turn, than a shake.

§ 5. The time of these Inventions was about the year 1658, as appears (among other evidence) from this inscription, upon one of the aforesaid double Ballance-Watch∣es, presented to K. Charles II, viz. Robert Hook inven. 1658. T. Tompion fecit 1675.

This Watch was wonderfully approved of by the King; and so the Invention grew into reputation, and was much talk∣ed of at home, and abroad. Particularly its same flew into France, from whence the Dauphine sent for two; which that eminent Artist Mr. Tompion made for him.

§ 6. Dr. Hook had long before this, caused several pieces of this nature, to be made, altho they did not take till after 1675. However he had before so far proceeded herein, as to have a Patent (drawn, tho not sealed) for these, and some other Contrivances, about Watches, in the year 1660. But the reason why that Patent did no further proceed, was some disagreement about some Articles in it, with some Noble Persons who were concerned for the procuring it. The same ingenious Dr. had also a Grant for a Pa∣tent for this last way of Spring Watches

in the year 1675: but he omitted the taking it out, as thinking it not worth the while.

§ 7. After these Inventions of Dr. Hook, and (no doubt) after the Publication of Mr. Hugens's book de Horolog. Oscil. at Paris 1673 (for there is not a word of this, tho of several other Contrivances) after this, I say, Mr. Hugen's Watch with a Spiral Spring came abroad, and made a great noise in England, as if the Longitude could be now found. One of these the Lord Bruncker sent for out of France, (where Mr Hugen•• had a Patent for them) which I have seen.

This Watch of Mr. Zulichem's agreed with Dr. Hook's, in the application of the Spring to the ballance: only Mr. Zuli∣chem's had a longer Spiral Spring, and the Pulses and Beats were much slower. That wherein it differs, is 1. The Verge hath a Pinion instead of Pallets; and a Contrate-wheel runs therein, and drives it round, more than one turn. 2. The Pallets are on the Arbor of this Contrate-wheel. 3. Then followeth the Crown wheel, &c. 4. The ballance, instead of turning scarce quite round (as Dr. Hook's) doth turn seve∣ral rounds every vibration.

§ 8. As to the great abilities of Mr. Hugens, no man can doubt, that is ac∣quainted with his Books, and his share in the Philosophical Transactions, &c. But I have some reason to doubt, whether his fancy was not first set on work, by some Intelligence he might have of Dr Hook's Invention, from Mr Oldenburgh, or others his correspondents here in England.

But whether or no that ingenious per∣son doth owe any thing herein to our in∣genious Dr Hook, it is however a very pretty, and ingenious contrivance; but subject to some defects: viz. When it standeth still, it will not vibrate, until it is set on vibrating: which, tho it be no defect in a Pendulum Clock, may be one in a Pocket-Watch, which is exposed to continual jogs. Also, it doth somewhat vary in its Vibrations, making sometimes longer, sometimes shorter turns, and so some slower some quicker vibrations.

I have seen some other contrivances of this sort, which I mention not, because they are of younger standing. But these two (of Dr Hook and Mr Hugens) I have taken notice of, because they were the first that ever appeared in the world.