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SYDNEY CHAPMAN; ESQ., M.A., D.SC, ON^ 



permission, he would like to say how privileged he felt himself to have 

 been in having spent much the greater part of his life as a member 

 of the staff of Greenwich Observatory. One thought which had often 

 been on his mind had been emphasized by Dr. Chapman's paper, 

 namely, the continuity of the work of Greenwich Observatory. 



It was more than 240 years since John Flamsteed became the 

 first Astronomer Royal, with full permission to provide himself 

 with what instruments he thought necessary at his own expense. 

 Amongst those instruments was a magnetic needle, the forerunner 

 of the magnetic observatory that was established by Airy 80 years 

 ago. Halley, the second Astronomer Royal, as Dr. Chapman had 

 told them, was one of the great, founders of the science of terrestrial 

 magnetism ; he was the first to make a magnetic chart of the world, 

 undertaking several voyages for that purpose. The latest magnetic 

 chart of the world was that to which, since the War began, Dr. Chap- 

 man had devoted himself at Greenwich Observatory. 



Airy had founded the magnetic department for the study of 

 magnetic variation, but when iron ships superseded those of wood, 

 and steamers the sailing vessels, fresh problems had to be solved. 

 The best way of dealing with the disturbance of the mariner's com- 

 pass — due to the presence in ships of great masses of iron, and of 

 powerful machinery in rapid motion — had to be sought out, and 

 Airy took a leading part in that work. Now when seamen had 

 learnt to rely upon the performance of their chronometers as thfi 

 simplest way of determining their longitude at sea, fresh difficulties 

 had arisen, for electric dynamos were part of the equipment of modern 

 vessels, and the magnetization of a chronometer or watch might 

 seriously affect its performance. 



When Dr. Chapman first came to the Observatory, seven years 

 ago, this had become a practical question : " What intensity of 

 magnetic field would alter the rate of a chronometer by one second 

 a day ? " and Dr. Chapman at once set to work to obtain the answer, 

 and he succeeded. His work at Greenwich Observatory had there- 

 fore been entirely on the lines of its historic continuity, and had 

 been of great practical importance to the nation. And that after- 

 noon he had given in short compass a complete review, admirably 

 clear and simple, of a wide subject, some branches of which were 

 quite new, and in which, moreover, he has himself been one of the 



