532 THE POPULAR SCIENCE MONTHLY. 



and known as an accomplished observer. It has always been thus ; 

 the scientific men who have been successively placed at the head of 

 this establishment were, at the time of their nomination, perfectly 

 familiar with the routine of their profession. They have all in like 

 manner devoted themselves with special zeal to the improvement of 

 instruments, and to the perfection of methods ; the result has been 

 that happy stability in principles, that continuity in labors, which is 

 the first condition for the success of researches destined to reveal to 

 us the slow variations that are going on in the system of the world. 



Greenwich is so much the more free to concentrate all its efforts 

 upon the astronomy of precision, as numerous observatories around it, 

 erected by opulent universities, or due to the enlightened initiative of 

 some rich proprietors and the great merchants of the city, share the 

 labors that the central establishment leaves out of its programme. 

 Oxford possesses an important observatory, founded in 1771, by the 

 aid of a legacy of Dr. Radcliffe, now under the direction of the Rev. 

 Robert Main, and the university has decided to found a second one. 

 Cambridge has the Trinity Observatory, that Mr. Airy directed from 

 1827 to 1835, and which is now intrusted to Mr. Adams ; the University 

 of Durham possesses also a very well-organized observatory, founded 

 by the city thirty years since. 



The observatory of Liverpool was created specially for the study 

 of marine chronometers. There, the numerous ships that enter the port 

 of the Mersey can have their timepieces regulated. The " chronometri- 

 cal chamber" is a vast sweating-room, warmed by steam; each of the 

 hundred marine-wntches that the observatory can study at the same 

 time is inclosed in a glass case, in which the air is still heated by a 

 gas-burner, supplied with a regulator, in order to be able to carry the 

 temperature successively from 10 to 18 and to 27 Centigrade. 

 After having tried in this chamber the chronometers that have been 

 intrusted to him by the marine, the observer returns them with the 

 table of their movements. 



The Edinburgh Observatory was built in 1818, on Calton Hill, 

 situated northeast of the city, Avhere there has been in existence since 

 the last century an old tower destined for observations of all kinds. 

 The foundation of this establishment was due in the beginning to an 

 astronomical society, organized for this purpose in the ancient capital 

 of Scotland ; but, not being able to pay for the instruments Ordered, 

 nor to appoint astronomers, it was decided in 1834 to yield the obser- 

 vatory to the Government. The first " astronomer royal for Scotland," 

 charged with the direction of the Edinburgh Observatory, was Hen- 

 derson, who returned there from the Cape of Good Hope. His succes- 

 sor, Mr. Piazzi Smyth, has established on Calton Hill a time-gun, a 

 cannon of twenty pounds, which, fired by means of an electric current 

 at one o'clock in the afternoon, signals the time to the mariners, and 

 sives them the means of resjulatin^ their chronometers. For some 



