In 1775 John Harrison made a critical remark about Graham’s dead beat escapement, saying, of George Graham, that “…either he must be out of his Senses, or I must be so!” Later in the same publication he stated of his own clock that “…there must be then more reason…that it shall perform to a second in 100 days…than that Mr Graham’s should perform to a second in 1.” Keeping time consistently to within one second in 100 days was a degree of accuracy not achieved until around a century and a half later by mechanical clocks such as Shortt’s free pendulum system.
Harrison published his remarks in a vitriolic and virtually impenetrable book, the manuscript and transcriptions of which are freely accessible online. On reading the book, which contains scattered descriptions of his method, the celebrated watchmaker Thomas Mudge, stated of Harrison that the book’s contents had “…lessened him very much in my esteem…” and that “…there are several things which he says about Mr Graham’s pallets and pendulum that are absolutely false… ”. The London Review of English and Foreign Literature described the work as “one of the most unaccountable productions we ever met with” and went on to say that “every page of this performance bears marks of incoherence and absurdity, little short of the symptoms of insanity”.
Harrison’s words were not taken seriously by any of his contemporaries and his radical statement about the capabilities of his pendulum clock, with its large pendulum arc, relatively light bob, and recoil grasshopper escapement, remained largely unexplored until the 20th century. Then, in 1977, a number of horological scholars, who became known as The Harrison Research Group, began to look at his theories afresh.
Martin Burgess’ Clock B is a product of this collaborative research and represents one of the most significant historio-technical investigations in recent years. Recently, numerous experiments have been tried on the clock at the Royal Observatory, Greenwich with exciting results.
To learn more about this intriguing project please join us for a special one-day conference on July 12 2014 at the NMM.