88 Master Minds of Modern Science 



of that name. He was the first man to weigh the earth ; 

 this he did in 1774. When travelling in Scotland, he 

 measured the deviation of a plumb-line from the vertical 

 caused by the attraction of the mountain Schiehallion. 

 Maskelyne did more work for navigation than any of his 

 predecessors, and it was during his long tenure of office at 

 Greenwich that the Government offered a reward of 

 twenty thousand pounds for a clock or watch that would 

 go perfectly at sea, notwithstanding the tossing of the 

 ship and the great changes of temperature to which it 

 might be subjected. 



This prize was won by John Harrison, a Yorkshireman 

 born in 1693, who as early as 1726 constructed a time- 

 keeper ' compensated ' against changes of climate. For 

 years he toiled at his time-keepers, until at last he made 

 a chronometer which in a voyage to Jamaica in 1761-62 

 determined the longitude within eighteen miles. But it 

 was not until 1773 that Harrison, then an old man, 

 received the full amount of the reward. His original 

 chronometer is still preserved at the Observatory, and not 

 long ago Commander Rupert Gould, R.N., succeeded in 

 making it go again after many years of rest. 



Maskelyne first published the long-desired Nautical 

 Almanac, and superintended its publication until his 

 death. He lived until 1811, and was succeeded by John 

 Pond, who was famous for the accuracy of his observa- 

 tions. He ran the Observatory with an iron hand, which 

 did not make his assistants either happy or useful. 



His successor was George Airy, perhaps the greatest 

 organizer who was ever in charge at Greenwich. Indeed, 

 he entirely reorganized and almost rebuilt the Observa- 

 tory ; he installed new telescopes, and it was under him 

 that photography began to play a part in astronomical 

 observation. The eye of the camera never tires, and it is 

 entirely by this means that the present marvellous star 

 charts of the heavens have been compiled. 



