Last month, in Part I of this story, I took a look at a vintage Girard-Perregaux pocket watch with a very unusual spherical balance spring. As I mentioned back then, the 19th century was something of a golden age for the evolution of precision timekeeping, and it was also a time when what you might call classical precision timekeeping was born, eventually flourished, and then gradually declined.
If that statement’s not to be immediately laughed off, I have to say what I mean by "classical" precision timekeeping. The fascinating thing about the period very roughly between 1800 and 1900 is that though a lot of fundamental refinements to precision timekeepers took place, there was not really any basic change in the materials used by watchmakers. In fact, they had been working with essentially the same stuff since the first portable watches and clocks were made way back in the early Renaissance: steel, brass, and (slightly later) jewels for bearings.
While a high-accuracy, late-19th-century pocket watch with a detent escapement and temperature-compensated balance can keep time to near-quartz accuracy (depending on how well it’s adjusted and how well you take care of it), it’s not, fundamentally, made of any different materials than could have been found in use 300 years earlier. In the early 20th century though, high timekeeping precision increasingly became a problem for metallurgists as well as for watchmakers, and today advances in mechanical horology, such as they are, continue to involve much more than watchmaking techniques and materials per se (and high-tech manufacturing techniques like silicon etching, LIGA, and spark erosion, which travel along with the fancy-pants materials).
In Part I, I looked at a pocket chronometer from 1860 with a spherical balance spring; in Part II, I’ll be examining another Girard-Perregaux pocket watch – this time, from a little later. Girard-Perregaux’s historian and museum curator, Willy Schweitzer, says it was completed around 1880.
The dial and case of the watch itself are what you’d expect from a good pocket watch of the era; in fact, the dial and hands are a little more ornate than you’d ordinarily expect from a precision watch of the 1880s or ’90s. Still, the quality of the case and the dial work would tend to make you think that something a little special is under the hood. And you’d be right.
This is a simple watch: time only, with no additional complications. However, it’s pretty obvious that making a portable machine to tell the time to a high degree of accuracy was very serious business indeed. This sort of watch would have been extremely expensive in its time and would have been owned and carried by someone wealthy enough to afford it, but also concerned enough with accuracy to pay quite a bit more for the very best in precision manufacturing and hand-adjusting, which, for a watch of this sort, would be a time-consuming process taking weeks rather than days.
Unlike the chronometer we looked at in Part 1, this watch has no fusée, the elimination of which allows a larger balance and a larger mainspring barrel than would have been possible with a fusée and chain. Also unlike the 1860 watch this one is wound and set by the crown, rather than with a key. Both watches have bimetallic, cut balances, which allow the balance to change its diameter in response to temperature changes in order to compensation for temperature-induced changes in the elasticity of the steel balance spring.
Though the lack of good sealing against dust means debris has built up inside the case (a problem with all watches, until the gradual development of modern gaskets and screwback cases in the 20th century) the movement is in an amazing state of preservation considering its age. At 12:00, just under the crown, is the crown wheel which rotates as the crown is turned when winding the watch; adjacent to it is the ratchet wheel for the mainspring barrel, which is prevented from unwinding rapidly (and destructively) by the click, situated at about 1:00; the tooth of the click is held in place by the long, beautifully shaped click spring. Click springs in vintage pocket watches often seem to have brought out the aesthete in watchmakers, although in this particular watch you could say the same about the entire movement.
Of course the most spectacular features of the movement are the golden bridge for the center wheel (center) and third wheel (at about 10:00) with its enormous ruby jewels, and the half golden bridge (a cock, really) for the fourth and escape wheels. Despite the softness of the material and the fact that they’re polished in such a way as to make even the slightest scratch stand out like magnesium flare on a moonless night, the two gold bridges are in remarkably good shape considering their age. Servicing this watch would have required great care on the watchmaker’s part to avoid leaving unwanted signs of intervention, although of course, not leaving things like scratches and marred screw slots is a minimum standard and a matter of course for a properly trained watchmaker.
Another relatively unusual feature is the detent escapement. The lever escapement, which was developed around the mid-18th century and is usually credited to the Englishman Thomas Mudge, and which is probably in the watch you’re wearing right now, works just fine but can start to wander off a steady rate if, or rather, when, the oils on the surfaces that get power from the escape wheel start to gum up. Back in the day, before modern synthetic lubricants, this was an even bigger problem (a year between cleanings was pushing it) and the detent escapement has the advantage of not needing oil.
The detent escapement has no lever to pass energy from the escape wheel to the balance; instead, it consists of a detent (hence the name) that locks the escape wheel and which is unlocked by the balance as it swings. When the detent is moved aside, the escape wheel unlocks and moves forward one tooth, catching the impulse jewel on the balance and giving it a push to keep it swinging. The detent escapement (which was also called a chronometer escapement) is prone to unlocking accidentally if jolted and isn’t as secure as the lever, so the lever was and is overwhelmingly preferred for portable timekeepers, but the detent was an option if you were a) wealthy enough to afford one, b) picky enough about timekeeping to desire one and, c) careful enough in your personal habits to know you weren’t going to be knocking the watch and making the escapement skip every five seconds.
Above, you can see the escape wheel itself (it’s gold, the better to resist magnetism) tucked under the balance. The watch isn’t wound, so there’s no power in the gear train but if there were, one of the escape wheel teeth would be held by torque in the gears against the small semicircular ruby approximately in the center of the picture.
As you can see, the escape wheel teeth are quite close to the center of the balance, and as the escape wheel turns clockwise, it pushes against the impulse jewel on the balance roller (which is the hub of the balance, more or less) pushing the balance in a counterclockwise direction. If you think about it a minute you’ll see that unlike the lever, the detent escapement only "gives impulse" in one direction which is a little bit of a disadvantage relative to the lever (George Daniels’s co-axial escapement is designed so as to need no oil, like the detent, but to provide the "safety" of the lever, and to give impulse in both directions as well).
Now let’s talk about that balance spring.
The balance spring is a pretty fancy piece of work. It’s not quite as out-there as the cylindrical balance spring we looked at in Part 1 but it’s still a gorgeous little thing, and the result of a number of careful operations; they were made basically by winding flattened wire around a cylindrical form, and then heat tempering to the cornflower blue you see here. The basic idea behind cylindrical balance springs was the same as that behind cylindrical springs or for that matter, the Breguet/Phillips overcoil: to keep the spring "breathing" symmetrically.
A flat balance spring will tend to make the pivots of the balance move side to side as it tightens and opens, which exaggerates the variation in rate between positions. The problem with the cylindrical balance spring is that it doesn’t really perform much better than a more conventional overcoil, and it adds a lot of height (for obvious reasons) so by the 20th century, you’d mostly find them in marine chronometers, where they persisted right up to the 1960s and even later.
One other point worth noting is the difference in size between the balance pivot, and the pivot for the center wheel. In the above image the balance pivot is very large and sitting in a jewel shaped to tolerate the considerable side-load created by the mainspring barrel. Yes, you want as little friction as possible, but the wheel only turns once an hour so you can (and should) use the largest possible pivot consistent with not overdoing it. On the other hand, the balance wheel pivot is needle-fine; you can just barely see it under the cap jewel.
Keep in mind that the balance is pretty massive relative to the diameter of the pivot and you can understand why dropping a pocket watch like this would mean a trip to a watchmaker. Even an inch or two drop onto a hardwood table could bend or break the pivots (and this helps us understand why shock protection systems, when they finally came along, were such a big deal and so important in the development of modern sports watches).
Establishing who invented what in watchmaking is always tricky, especially the further back you go but John Arnold was granted a patent for the cylindrical balance spring in 1776, and you can see one of his below – this is a pocket chronometer, from 1781, with an early form of the temperature-compensated balance.
Cylindrical balance springs today continue to be rare, for all the same reasons they were rare Back In The Day – they’re much harder to make; they add height; they don’t give you any major advantage you couldn’t get from a Philips/Breguet overcoil. However, a few companies continue to experiment with them – Montblanc, Jaeger-LeCoultre (which has also deployed a spherical balance spring), Christophe Claret, and Chopard have all introduced watches with cylindrical springs, albeit in very, very low numbers.
When I think of Girard-Perregaux today, and its history, I think on the one hand of the company that made solid, mid-range wristwatches in the post-World War II era and, on the other hand, of the company that made the ultra-high accuracy Chronometer HF (one of the first high-beat wristwatches) and which, a little further back, made amazing pocket chronometers like this one (as well as more than their fair share of tourbillon pocket chronometers as well). It’s no secret that GP has, in recent decades, struggled to establish a clear, consistent image in the minds of consumers but the material and history is all there.
This particular watch really embodies that cornball cliché, "the fascination of mechanics," to a T; it’s devoted single-mindedly to one end, which is precision timekeeping, but the emotional commitment to excellence that’s part of that very much manifests itself as well in the unnecessary but in another way, essential, beauty of the movement. That’s a hard thread to follow. Nowadays, there are more companies losing it than not, for various reasons. What I’d want for Girard-Perregaux today is for whoever’s in charge to look at something like this, see how the movement aesthetics and functionality are two sides of the same coin, and take that as an inspiration moving forward. Come to think of it, that wouldn’t be a bad thing for Swiss watchmaking in general.
In case you missed it, here’s Part I. For a look at two examples of high grade pocket chronometers from about a century earlier, check out these two from the English masters Arnold and Earnshaw here. To see the modern Girard-Perregaux collections visit girard-perregaux.com.