COMMON THINGS TIME. 



of Longitude to sanction it. These apprehensions, however, proved 

 groundless, for the change took place unperceived by the great 

 mass of the people. 



Meanwhile the watch and clockmakers rejoiced at the change 

 which established a sort of civil time, in accordance with which 

 it was mechanically possible to construct timepieces. Such a 

 change relieved them from the annoyance produced by the remon- 

 strances of their customers complaining of their best constructed 

 watches losing or gaining as much as a quarter of an hour, or 

 even more, upon the sun. It was in vain that the celebrated 

 Breguet, and his colleagues of the trade, assured them that the 

 sun and not the watch was too fast or too slow. 



40. It may be easily imagined how utterly incompatible with the 

 management of public business as now conducted such an imperfect 

 system of chronometric regulation would be, when it is considered 

 what disastrous consequences might arise upon railways, if the 

 starting, stopping, and arrival of trains, were not subject to greater 

 precision than could be attained under such circumstances. 



41. However exactly the chronometric measures in a given 

 place may be regulated, their indications will necessarily differ 

 from those of similar chronometric measures in other places 

 having different longitudes. The cause of this difference is 

 the successive arrival of the mean sun at the several meridians 

 of such places. By the apparent diurnal motion of the heavens, 

 the sun, earned round the globe, arrives in succession, from hour 

 to hour, at the meridians of places situate one westward of the 

 other, and as the sun thus carried round makes a complete revolu- 

 tion in 24 hours, it moves from meridian to meridian at the rate 

 of 360 in 24 hours, or 15 per hour, or 1 in four minutes. Thus, 

 at two places differing in their longitude by 1, the local time will 

 differ by four minutes, that which is east being four minutes 

 earlier than that which is west. 



In consequence of this the clocks in different towns of the 

 United Kingdom show at the same moment of absolute time 

 different hours. Liverpool, for example, being 3 west of London, 

 and 1 being equivalent to four minutes, it follows that the sun 

 passes the meridian of London twelve minutes before it passes 

 that of Liverpool ; and as this is equally true of the fictitious sun 

 which regulates civil time, it follows that mean noon at London, 

 and therefore all other hours determined with relation to mean 

 noon, precede the corresponding hours at Liverpool by twelv 

 minutes. 



42. It has been lately proposed to assimilate the chronome 

 epochs at all parts of the United Kingdom, by means of cloc 

 which are moved with a common motion, so that their han 



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