Sir Frank Dyson 89 



Airy was a strong man, perhaps somewhat selfish, but 

 he placed the work of the Observatory before all personal 

 considerations. We may quote words from his auto- 

 biography : 



The Observatory was expressly built for the aid of astronomy 

 and navigation, for promoting methods of determining longitude 

 at sea, and more especially for determination of the moon's 

 motions. All these imply, as their first step, the formation of 

 accurate catalogues of stars and the determination of the 

 fundamental elements of the solar system. ... It has been 

 invariably my own intention to maintain the principles of the 

 long-established system in perfect integrity, varying the instru- 

 ments and the modes of employing them ... as the progress 

 of science might require. 



It is to Airy more than any of those who preceded him 

 that the great reputation of Greenwich Observatory is 

 due. A famous foreign astronomer once said : 



Greenwich Observatory has, during the past century, been so 

 far the largest contributor to the determination of geographical 

 positions on sea or land that if this branch of astronomy were 

 entirely lost it could be reconstructed from the Greenwich 

 observations alone. 



In 1836 Airy proposed the creation of the magnetic 

 and meteorological department of the Observatory, with 

 a system of regular two-hour observations. It was from 

 this small beginning that we now have our marvellous, 

 world-wide system of weather forecasting, which grows 

 and improves with each successive year. Airy again it 

 was who in 1873 formed the solar photographic depart- 

 ment, to which was presently added the spectroscope, that 

 simple yet marvellous instrument by which light is 

 analysed and the composition of the heavenly bodies 

 studied. 



One of the many remarkable uses of spectrum analysis 

 is that we are able thereby to measure the rate of approach 



