In the High Street there is a slate plaque marking the site of the former laboratory of Robert Boyle and Robert Hooke. Robert Boyle (1627-1691) was the son of the Earl of Cork and is best known for Boyle's law, which states the inversely proportional relationship between the volume and pressure of a gas, and its experimental proof. In the Skepticall Chymist (1661) he gave a modern, as opposed to an Aristotelian, definition of the term "element". Boyle's request to his assistant Robert Hooke resulted in a design for a modern air pump, with which he was able to study the vacuum, respiration, and combustion. The seventeenth-century gossip John Aubrey says of Boyle: "He is very tall ... and streight, very temperate, and vertuouse, and frugall: a Batcheler ... his greatest delight is Chymistrey. He haz at his sister's a noble Laboratory, and severall servants (Prentices to him) to looke to it ... His Works alone may make a Librarie." Boyle was strongly influenced by Francis Bacon and, like Bacon, he believed that science was for practical application. Robert Hooke (1635-1703) was an experimental scientist, mathematician, architect, and astronomer. Secretary of the Royal Society from 1677 to 1682, he is remembered for the discovery of the proportional relationship of the extension of a spring and the force applied to produce that extension. He was a chorister at Christ Church, and while at Oxford was an assistant to Robert Boyle. In 1662 Hooke was appointed the first curator of experiments to the Royal Society. His manifold scientific activities included the discovery that thermal expansion is a general property of matter, and he designed a balance-spring for watches, a new type of reflecting telescope, the first compound microscope, and the wheel barometer. His work Micrographia of 1665 contained his microscopical investigations, which included the first identification of biological cells. Hooke became involved in a dispute with Isaac Newton over the priority of the discovery of the inverse square law of gravitation. Although he communicated some form of inverse square law to Newton, modern opinion is that credit for the law of universal gravitation must go to Newton. Hooke was also an architect, and helped rebuild London after the Great Fire of 1666. Aubrey held his ability in high regard: "He is certainly the greatest Mechanick this day in the World." In the High Street is also the entrance to University College. Stephen Hawking, famous for his work on black holes and other aspects of cosmology, was an undergraduate here. The story goes that he did not do exceptionally well in his final exams. He was given a viva to determine whether he would obtain a first or second class degree. The examiners asked Hawking what he would do after graduating. He replied that if they gave him a first he would go to Cambridge to do research; otherwise he would stay in Oxford. He was given a first, and the rest is history. In the Great Quad of All Souls College you can see a marvellous sundial, designed by Christopher Wren (1632-1723). Best remembered now as an architect - in Oxford he was responsible for the Sheldonian and the Tom Tower in Christ Church - Wren was also a mathematician and astronomer. He was elected a Fellow of All Souls in 1653, and was Savilian Professor of Astronomy from 1661 to 1673. As we shall see, he played a leading role in the formation of the Royal Society, England's foremost scientific institution. Another notable Fellow of All Souls was the Elizabethan mathematician Robert Recorde, who introduced the equals sign into English mathematics in his book The Whetstone of Witte of 1557.