John Wallis, Christopher Wren 51 



father, who had been elevated to the peerage by Charles I. 

 Brouncker, after obtaining the degree of Doctor of Physic 

 in the University of Oxford, devoted himself to the study 

 of mathematics, and acquired a great reputation at home 

 and abroad by his investigations, which take a high rank 

 in the history of the subject. He made extensive use of 

 approximation by infinite series, and though he is not the 

 originator of continued fractions, he first used them 

 effectively. He was one of the original promoters of the 

 Royal Society, and was named as its President in the Charter. 

 He occupied that position for fifteen years, during which 

 he assiduously devoted himself to its duties. The first years 

 of the Society were necessarily critical ones, and much 

 credit for the judicious and successful direction of its affairs 

 is due to his distinguished services. 



Christopher Wren (1632-1723), though known to fame 

 mainly as a great architect, distinguished himself at Oxford 

 as a mathematician. He had, independently of Newton, 

 suggested the existence of a universal attraction as the 

 cause which retained planets in their orbits, and is highly 

 spoken of in the " Principia." He also was the first to 

 calculate the length of the curve called the cycloid. 



In 1657 he became Professor of Astronomy at Gresham 

 College, and three years later took over the Savilian Profes- 

 sorship at Oxford. Wren's contributions to science were 

 substantial. When the Royal Society expressed a wish 

 that mathematicians should investigate the laws of impact, 

 Huygens, Wallis and Wren sent in independent investiga- 

 tions. All these contained a correct appreciation of the 

 principle of conservation of momentum. The great archi- 

 tect's solution was correct so far as perfectly elastic bodies 

 were concerned. Wallis began with the consideration of 

 inelastic bodies, but ultimately treated the problem in the 

 most general manner, including both perfect and imperfect 

 elasticity. 



A most striking instance of a family, who in many 

 successive generations reached distinction in the academic 

 world, may here be recorded. James Gregory (1638-1675), 

 educated at Aberdeen, published, at the age of twenty- 

 five, a treatise on optics, containing the invention of the 



D 2, 



