90 Master Minds of Modern Science 



or recession of a star. For instance, we know that 

 Arcturus is hurrying away from the solar system at a 

 rate of about twenty miles a second, while another star 

 is approaching our system at the terrific speed of about 

 fifty-five miles a second. 



Airy was the first Astronomer Royal to busy himself 

 with important work outside the Observatory. On three 

 occasions he made long journeys to study eclipses of the 

 sun ; he went to America to help in settling the boundary 

 between Canada and the United States ; and he made an 

 expedition to Harton Colliery, near South Shields, in order 

 to study the decrease in gravity observable in the descent 

 of a deep mine. 



Airy lived to be over ninety. He was succeeded by 

 W. H. M. Christie, who did a great deal in setting up new 

 instruments, including two fine new telescopes. During 

 his period the new library was built, as well as the Transit 

 Pavilion and the Magnetic Pavilion out in the Park. The 

 Observatory has indeed grown greatly since its founda- 

 tion by Charles II. Flamsteed's little domain was only 

 twenty-seven yards long by fifty deep, and consisted of 

 little more than a dwelling-house with one fine room, 

 the original ' observatory/ above it. To-day the en- 

 closed ground measures about two hundred yards by 

 sixty, and contains a large number of buildings and a 

 garden. 



We have all heard of ' Greenwich time/ which sets the 

 standard not only for Britain, but for the world. One 

 of the most interesting places in the Observatory is the 

 room in which are kept the clocks. This room has double 

 doors and is kept at a constant and rather warm tempera- 

 ture. The special clock is the Short t clock made by the 

 Synchronome Company. It is a two-clock combination, 

 a free pendulum on one wall electrically connected with 

 a slave clock on another wall. The mechanism is far too 

 intricate for the writer to describe. It is enough to say 



