H. C. Sorby, J. Waterston, G. Airy 165 



a slip of calculation preventing the correct result being 

 obtained. 



Of Waterston's life very little is known. He was born 

 in Edinburgh in 1811, and showed great aptitude for mathe- 

 matics while at the High School of that town. He then 

 became Naval Instructor in the service of the East India 

 Company. After his retirement he lived in various towns 

 of Scotland, and finally at Edinburgh. One evening in the 

 spring of 1884, he left his lodgings for his evening walk, and 

 was never seen again. It is supposed that he went to Leith 

 to look at a new breakwater which was being constructed 

 there, and that he accidentally fell into the water and was 

 swept away by the tide ; but this rests on surmise only. 



Among professional British astronomers during the last 

 century four men stand out prominently : Sir George Airy, 

 Sir John Herschel, John Crouch Adams, and Sir David Gill. 

 When Airy was called to take charge, first of the Observatory 

 of Cambridge and later of the Royal Observatory at Greenwich, 

 he had already made his name famous by his mathematical 

 and optical investigations, which have been mentioned in 

 connexion with his career at Cambridge. In astronomy he 

 proved himself to be equally eminent as an administrator and 

 investigator. He introduced revolutionary reforms in the 

 practice of observatories by insisting on a rapid reduction 

 and publication of all observations. After his appointment as 

 Astronomer Royal, he set to work at once to reduce the series 

 of observations of planets which had accumulated during 

 eighty years without any use having been made of them. 

 This was followed up by a similar reduction of 8,000 lunar 

 observations. He was equally energetic in adding to the 

 instrumental equipment. When Greenwich was first founded, 

 the longitude determination at sea depended to a great extent 

 on measuring the distance between stars and the moon. Hence 

 accurate tables of the position of the moon were essential, and 

 the preparation of these tables has always been considered 

 to be the chief care of Greenwich. The observations were made 

 with a transit telescope which could only be used when the 

 moon was passing the meridian, until Airy in 1843 persuaded 

 the Board of Visitors to take steps for constructing a new 

 instrument which would enable him to observe the moon 



