$ 2c S , 206] Hattey 257 



astronomers to pay careful attention to the effects to be 

 observed during a total eclipse of the sun, and in the 

 vivid description which he wrote of the eclipse of 1715, 

 besides referring to the mysterious corona, which Kepler 

 and others had noticed before (chapter VH., 145), he 

 called attention also to " a very narrow streak of a dusky 

 but strong Red Light," which was evidently a portion of 

 that remarkable envelope of the sun which has been so 

 extensively studied in modern times (chapter xin., 301) 

 under the name of the chromosphere. 



It is worth while to notice, as an illustration of Halley's 

 unselfish enthusiasm for science and of his power of looking 

 to the future, that two of his most important pieces of work, 

 by which certainly he is now best known, necessarily 

 appeared during his lifetime as of little value, and only 

 bore their fruit after his death (1742), for his comet only 

 returned in 1759, when he had been dead 17 years, and 

 the first of the pair of transits of Venus, from which he 

 had shewn how to deduce the distance of the sun, took 

 place two years later still ( 227). 



^ 206. The third Astronomer Royal, James Bradley, is 

 popularly known as the author of two memorable dis- 

 coveries, viz. the aberration of light and the nutation 

 of the earth's axis. Remarkable as these are both in 

 themselves and on account of the ingenious and subtle 

 reasoning and minutely accurate observations by means of 

 which they were made, they were in fact incidents in a long 

 and active astronomical career, which resulted in the 

 execution of a vast mass of work of great value. 



The external events of Bradley's life may be dealt with 

 very briefly. Born in 1693, he proceeded in due course 

 to Oxford (B.A. 1714, M.A. 1717), but acquired his first 

 knowledge of astronomy and his marked taste for the 

 subject from his uncle James Pound> for many years rector 

 of Wansted in Essex, who was one of the best observers of 

 the time. Bradley lived with his uncle for some years after 

 leaving Oxford, and carried out a number of observations 

 in concert with him. The first recorded observation of 

 Bradley's is dated 1715, and by 1718 he was sufficiently 

 well thought of in the scientific world to receive the honour 

 of election as a Fellow of the Royal Society. But, as his 



