It became at once necessary to settle upon one uniform system of time for use in the railway guides. Apart from this, a passenger taking train, say, at Swindon, might have been very troubled to know whether the advertised time of his train was that of Exeter, the place whence it started, or Swindon, the station where he was getting in, or London, its destination. 'Railway time,' therefore, was very early fixed for the whole of Great Britain to be the same as London time, which is, of course, time as determined at Greenwich Observatory. At first it was the custom to keep at the various stations two clocks, one showing local time, the other 'railway,' or Greenwich time, or else the clocks would be provided with a double minute hand, one branch of which pointed to the time of the place, the other to the time of Greenwich. It was soon found, however, that there was no sufficient reason for keeping up local time. Even in the extreme West of England the difference between the two only amounted to twenty-three minutes, and it was found that no practical inconvenience resulted from saying that the sun rose at twenty-three minutes past six on March 22, rather than at six o'clock. The hours of work and business were practically put twenty-three minutes earlier in the day, a change of which very few people took any notice. Other countries besides England felt the same difficulty, and solved it in the same way, each country as a rule taking as its standard time the time of its own chief city. There were two countries for which this expedient was not sufficient--the United States and Canada. The question was of no importance until the iron road had linked the Atlantic to the Pacific in both countries. Then it became pressing. No fewer than seventy different standards prevailed in the United States only some twenty years ago. The case was a very different one here from that of England, where east and west differed in local time by only a little over twenty minutes. In North America, in the extreme case, the difference amounted to four hours, and it seemed asking too much of men to call eight o'clock in their morning, or it might be four o'clock in their afternoon, their noonday.