George Graham was born in Cumberland, England in 1673.  He moved to London, and was apprenticed to Henry Aske for the customary seven years. He was admitted to the clockmaker's company in 1695, and went to work for Thomas Tompion, where upon he become Tompion's partner and successor:

George Graham, nephew of the late Mr. Thomas Tompion, who lived with him upward to 17 years, and managed his trade for several years past, whose name was joined with Mr. Tompion's for some time before his death, and to whom he left all his stock and work, finished and unfinished, continues to carry on the said trade at the late dwelling house of the said Mr. Tompion, at the sign of the Dial and Three Crowns, at the corner of Water Lane in Fleet Street, London, where all persons may be accommodated as formerly.

London Gazette, November 28, 1713.

In this period it was discovered that clocks ran faster in cold weather, and slower in warm weather, although the effect was masked by the fact that the crude animal-based fats available for clock lubricants speeded them up by applying more power to the pendulum when they thinned out at higher temperatures. In fact, many early pendulum clocks keep better time now than when they were new because of modern clock oil, and temperature controlled environments.  

It was, in fact, Graham's invention of a clock escapement that was less dependent on train power, that isolated the temperature problem.  It has been said that Tompion invented the dead-beat escapement, but none the less it was Graham who perfected and named it, and to him goes the credit.

(image credit: brendlers.net)

The 'scape wheel rests on a pallet that is "dead": on the circumference of a circle centered at the verge pivot, so that when the pendulum is swinging the scape wheel tooth doesn't move backward (recoil) or forward (draw).  This was more important than it looks.  It was the first time that the two functions of an escapement, impulse, where the pendulum gets it's push, and locking, where the number of swings are counted, were separated, and this was the key to future escapement improvements.

With the pendulum now somewhat free of influence of the clock train, the problem of temperature changes became clear.  The expansion of metals with temperature increase was smaller than could be measured at the time, but the cumulative effect showed in the clock's change in rate.

Modern engineering texts will tell you that steel has an linear expansion of .00000633 per unit per degree f. That's hard to measure, even with modern measuring tools.  It was, however, known that different metals expanded at different rates, and graham put this to work.  The metal with the greatest expansion is mercury, and graham formed a pendulum with a jar full of mercury in place of the pendulum. This had the benefit of being adjustable, (more mercury in the jar would increase the compensation) as well as massive: Mercury has a higher weight per volume than lead.  It was realized early on that massive pendulums kept better time than light ones, because they resist small disturbances, and average out large ones.

I can't find a picture of a Graham pendulum, but here is one from a later regulator:

(image credit: Precision Pendulum Clocks    Derek Roberts   Exhibition catalog  1986)

This is a early 19c regulator by Thwates and Reed, a large maker.  

Here is a fine Graham longcase clock from the Vitale collection:

(image credit: The Vitale Collection Part II,   Christie's auction catalog Nov. 26, 1996)

As the successor to Tompion, Graham's workmanship was of the highest caliber: often better than Tompion's own, as these images show.

We'll end today's discussion on George Graham with a fine month duration longcase regulator, with high count pinions, dead beat escapement, and bolt-and-shutter maintaining power:

(image credit: St. Edmundsbury, UK, Manor House Museum)

Next time: 18th century clockmaking in other European countries.

Previously:

Monastic alarms and the beginnings of clockmaking
De Dondi's remarkable astrarium
Early tower clocks
Gothic iron clocks
Rennaisance clocks
Early english lantern clocks
Huygens and the pendulum
Fromanteel's English pendulum clocks
Huygens in Paris
Clement and the recoil escapement
Edward East and the golden age
Thomas Tompion
Daniel Quare
Joseph Knibb
Golden age recap
The balance spring
Paris - Louis Quatorze
Paris - La Regence