Question: who was the head of the royal society of london when halley came home to sell his map of the stars

title: Edmond Halley
text: Halley spent most of his time on lunar observations , but was also interested in the problems of gravity . One problem that attracted his attention was the proof of Kepler 's laws of planetary motion . In August 1684 , he went to Cambridge to discuss this with Isaac Newton , much as John Flamsteed had done four years earlier , only to find that Newton had solved the problem , at the instigation of Flamsteed with regard to the orbit of comet Kirch , without publishing the solution . Halley asked to see the calculations and was told by Newton that he could not find them , but promised to redo them and send them on later , which he eventually did , in a short treatise entitled , On the motion of bodies in an orbit . Halley recognised the importance of the work and returned to Cambridge to arrange its publication with Newton , who instead went on to expand it into his Philosophiæ Naturalis Principia Mathematica published at Halley 's expense in 1687 . Halley 's first calculations with comets were thereby for the orbit of comet Kirch , based on Flamsteed 's observations in 1680 - 1 . Although he was to accurately calculate the orbit of the comet of 1682 , he was inaccurate in his calculations of the orbit of comet Kirch . They indicated a periodicity of 575 years , thus appearing in the years 531 and 1106 , and presumably heralding the death of Julius Caesar in a like fashion in − 44 ( 45 BCE ) . It is now known to have an orbital period of circa 10,000 years .