THE ELECTRIC TELEGRAPH. 



signal given daily at one in the afternoon, by the fall of a large 

 hall upon the dome of the Koyal Observatory at Greenwich.* 

 This being generally visible from a considerable extent of the 

 river below London-bridge, masters of vessels observing it can 

 regulate their time-pieces or note their errors. This system of 

 signals is in progress of extension. By means of a galvanic clock 

 at the Observatory, and the conducting wires which connect that 

 building with the station of the Electric Telegraph Company at 

 Lothbury, hourly signals giving accurately Greenwich time are 

 transmitted to the offices of the company at Lothbury, and in the 

 Strand opposite Hungerford-market. Similar signals are trans- 

 mitted several times a day to Tunbridge, Deal, and Dover by the 

 wires of the South-eastern Company. Signal balls are let fall 

 over the dome of the Telegraph Office in the Strand and at an 

 elevated station, Liverpool, at the same instant with the fall of 

 the ball over the Greenwich Observatory. Besides this time- 

 signals are transmitted on the wires twice a day, at 10 in the 

 forenoon, and 1 in the afternoon, directly from Greenwich to 

 various chief stations upon the system of lines of the Electric 

 Telegraph Company. 



267. From the first instant of the laying of the wires con- 

 necting the Greenwich Observatory with the stations of the South- 

 eastern Railway Company and the Electric Telegraph Company, it 

 was evident that one of the earliest and most useful applications of 

 them would be the determination of the longitudes of several of 

 the principal observatories in the British Isles and on the Con- 

 tinent. During the year 1853, the earliest opportunities were 

 accordingly taken for determining the longitudes of Cambridge, 

 Edinburgh, and Brussels, which was accomplished with complete 

 success, as far as regards the galvanic communications and the 

 observations of the signals at all the observatories. 



The observatories of Greenwich, Brussels, and Paris are now 

 placed in direct electric connection by the submarine cables 

 between Dover, Calais, and Ostend, to the great advantage and 

 advancement of astronomical science. 



268. In the routine of .the business of an observatory, the astro- 

 nomical clock is an instrument in never ceasing use. A part of 

 almost every astronomical observation consists in noting with the 

 last degree of precision the moments of time at which certain 

 phenomena take place ; and so great is the degree of perfection to 

 which the art of observation has been carried, that well-practised 

 observers are able, by the combination of a quick and observant 

 eye and ear, to bisect a second, and even to approach to a still 



* See Tract on Latitudes and Longitudes. 

 98 



