One of the most extraordinary features of Hooke was the prolific number of inventions that are attributed to him. These are referred to in his diary [18], the History of the Royal Society [2], and Hooke’s various writings. Some authorities state that his inventions number over 1,000. It was noted above that Hooke showed an interest in engineering from an early age, and Fig. 4.3 in Chap. 4 with its drawings of the components of the air pump clearly shows Hooke’s interest in the technical features of the machine.

Timekeeping. This was a major interest of Hooke. First he worked extensively on the pendulum which was also an interest of other scientists at the time such as the Dutchman Christiaan Huygens (1629–1695). Hooke studied the isochronicity of the simple pendulum, that is the conditions under which its period remained constant. For example, he studied the effect of altitude and gravity on the period of swing. He also worked extensively on the conical pendulum in which the bob describes a circle. A particularly interesting invention was Hooke’s so-called long pendulum. The entry for May 6, 1669 in the History of the Royal Society [2] states that “Mr. Hooke produced a new kind of pendulum of his own invention, having a great weight appendant to it, and moved with a very small force; viz. by such a contrivance, that a pendulum of about fourteen feet long, so as a single vibration of it is made in two seconds, with an excussion [excursion] of half an inch or less, having a weight of three pounds hanging on it, and moved by the sole force of a pocket watch… shall go 14 months…”. It seems very counterintuitive that such an enormous pendulum could be maintained swinging for so long by means of the minute power of a pocket watch but this is the case. There is a working model of this pendulum in the Science Museum in London, and the author made a smaller model 12 feet long which is swinging in his study.

Of more practical importance was Hooke’s invention of a pocket watch in which the mechanism was a coiled spring attached to the arbor of the balance. However this became a topic of great controversy. The history is complicated but Hooke apparently considered taking out a patent early on but held back because of a technical issue. Some 15 years later Huygens had the same idea and did acquire a patent which annoyed Hooke immensely. There was a great deal of controversy which even involved the king himself. In fact many scholars now believe that Hooke did have priority with this critically important development in timekeeping. One of the reasons for its importance was that it could be used to determine the longitude of a sailing ship. This depended on having an accurate timepiece so that the time when the sun reached its zenith could be accurately determined. From this the longitude was easily determined. Clocks in which the rate was determined by a pendulum were generally not accurate on a ship because of the rolling motion.

Hooke’s interest in the properties of springs has already been alluded to. He is credited with inventing the spring balance which is still extensively used. Here the weight in the pan determines the extension of the spring, that is, as the weight so the extension (in Latin, ut pondus, sic tensio). Later this was modified to Hooke’s law, that is the extension of the spring is determined by the force (ut tensio, sic vis).