William Hamilton Shortt, 1882-1971, spent all his working life in the employment of the London and South Western Railway and its successors. In 1908 one of the main problems with trains was to establish their safe speed on curved tracks. An accurate time standard was required which Shortt devised. In 1910 he met Frank Hope-Jones who offered him facitities for making experimental models. Many designs were produced before Shortt invented his 'hit-and-miss' synchroniser for a slave clock and his Free Pendulum.
In 1921 Shortt set up his first Free Pendulum vacuum clock at Edinburgh Observatory; its results astounded the world with revolutionary timekeeping confirmed at a rate of less than one second a year. By 1924 he had made an example for the Helwan Observatory in Egypt and five years later made the present example; in all he made 99 of these clocks for observatories, instutions and scientists all over the world. For his work Shortt was awarded the gold medal from the British Horological Institute in 1929, and made a Fellow in 1932. In 1954 The Clockmakers' Company awarded him the very first Tompion Medal.
This particular clock (along with two others numbered 21 & 22), were calibrated for mean time and specifically ordered by Mr A.L. Loomis of Tuxedo Park, New York. Loomis experimented with the method of time measurement by micro-chronograph using his three Shortt clocks. One very good reason for this experimentation was that with the advent of such an accurate timekeeper there became an immediate need to invent a more accurate method of measuring their accuracy. Furthermore Loomis realised that these clocks were capable of far greater feats and one such was to establish the effects on 'time' by the nutation of the earth. In the dictionary a nutation is a periodic oscillation of the earth's poles or in plain terms, the earth's wobble. The variations and their consequent effect on timekeeping were caused by the moon's gravitational pull and not surprisingly this could not be measured by a clock whose pendulum was itself based upon gravity. Also whilst nutation would require an accuracy of one second a day to reveal it, a lunar period would require ten thousandths. Loomis used Shortt's three clocks, which he bolted to the rock in the basement of Tuxedo Park, and compared them with a quartz crystal clock which was independent of gravity. The intricacies of the experiment are well described in Electrical Timekeeping, op. cit. but the result was that through the accuracy of the Shortt clocks the lunar period was showing a maximum and minimum of 2/10,000ths of a second.