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532 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 "chronometrical chamber" is a vast sweating-room, warmed by steam; each of the hundred marine-watches 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, where 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 observatory to the Government. The first "astronomer royal for Scotland," charged with the direction of the Edinburgh Observatory, was Henderson, who returned there from the Cape of Good Hope. His successor, 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 gives them the means of regulating their chronometers. For some