NA TURE 



[Nov. 6, 1884 



held at Rome about a year ago, and the recommenda- 

 tions then formulated have since been further considered 

 at a special International Conference recently assembled 

 at Washington, the delegates at which, in some cases 

 scientific men, in others the ambassadors accredited to 

 the United States, were instructed by their respective 

 Governments specially for the settlement of the questions 

 of a prime meridian and universal time. Their final 

 recommendations on the principal points involved are 

 now before the world. 



Unlike the related question of weights and measures, 

 that of time becomes to a great extent simplified by the 

 circumstance that no assimilation of units is necessary, 

 since in the reckoning of time there exists one natural 

 unit which already all nations alike employ, that of the 

 solar day, divided in all centres of civilisation into 

 twenty-four hours, each hour into sixty minutes, and each 

 minute into sixty seconds, and reckoned generally from 

 midnight to the midnight following. In the business and 

 concerns of any single centre no anomaly arises, but if 

 we travel to the east or west of our centre, say from 

 Greenwich, we change — not our manner of counting time 

 — not our unit — but only the zero from which we begin 

 to count, that is, midnight in our new position will occur 

 at a different absolute time. Thus midnight at Paris 

 occurs nine minutes of time before midnight at Green- 

 wich, and this difference between the natural time of the 

 two places is their difference of longitude. 



The practical navigator carries with him charts on 

 which longitude is marked as reckoned from some par- 

 ticular meridian. Whilst some nations use the Green- 

 wich meridian, others employ that of their own capital 

 city or observatory, so that longitudes become differently 

 reckoned on the charts of different nationalities. This, as 

 regards practical navigation and in many questions of 

 geography, was one inconvenience. 



For many years all clocks throughout Great Britain 

 have been regulated to Greenwich time. This causes no 

 appreciable inconvenience in other parts of the countrv, 

 because, on account of its small extent in the easterly and 

 westerly direction, the natural time at any place (as 

 referred to the sun) differs so little from Greenwich time 

 that no violence is done to our conceptions of morning 

 and evening as referred to the clock, whilst the advantage 

 of having one standard time throughout the country is, in 

 these days, enormous. Similarly the time of Paris is 

 used in France, and so on. In the United States of 

 America a more natural division into sections has been 

 made, each having its own standard time, about which 

 we shall have more to say further on. The standard time 

 thus used throughout each particular country or section 

 of country, whilst satisfying entirely internal needs, fails, 

 on account of the difference existing between the standard 

 times of adjacent countries, to meet international re- 

 quirements, not only in questions of scientific interest, but 

 also in matters commercial. The standard time counted 

 in any district must continue to regulate its civil affairs, 

 but for the efficient control of those of international con- 

 cern, such as the railway, telegraphic, postal, and steam- 

 ship services, an extension of the same principle to the 

 whole globe by the establishment of some system of 

 universal time, for use in conjunction with local standard 

 time, became very desirable, for although such universal 

 time could not be suitably employed in the ordinary way, 

 the importance of its adoption in matters of international 

 interest had become abundantly apparent. One other 

 point. In civil affairs the day is counted from midnight, 

 whilst astronomers count from the noon following, render- 

 ing troublesome conversions from one system to the other 

 frequently necessary. These were other questions re- 

 quiring consideration. 



Clearly therefore the time had come for promoting a 

 better understanding on points of this kind. The re- 

 commendations of the Roman Conference briefly stated 



were, that the initial meridian should be that of Greenwich, 

 corresponding to the point midway between the piers of the 

 Greenwich meridian circle, since such meridian fulfilled 

 all the requirements of science, being already that most 

 used and best likely to be generally accepted ; also that 

 longitude should be counted from the meridian of Green- 

 wich in one direction only, from west to east, that is to 

 say, the longitude of Berlin would be oh. 54m., and that 

 of Dublin 23I1. 35m. The Conference further recom- 

 mended, for purposes for which universal time would be 

 convenient, that the universal day should commence at 

 mean noon of Greenwich time, and be counted from oh. 

 to 24I1., as was proposed in America in the year 1879 

 by Sandford Fleming and Cleveland Abbe, a proposi- 

 tion which had received the support also of well-known 

 astronomers. It may be added that a proposition to 

 assimilate the astronomical day with the civil day, and 

 adopt it as the universal day, being scantily supported, 

 was lost. 



So far as regards the Roman Conference. Their pro- 

 posals served to indicate the points requiring consider- 

 ation, so that, attention having been thus directed to the 

 whole question during the year since elapsed, the dele- 

 gates attending the recent Washington Conference had 

 full opportunity of forming deliberate opinion thereon. 

 We are not yet in possession of the full discussions of the 

 Conference, but we know their decision on all essential 

 points. The recommendation of the Roman Conference 

 that the meridian of Greenwich should be the universal 

 prime meridian was confirmed. But on the question of 

 reckoning longitude the Conference resolved that it 

 should be counted from Greenwich in two directions up 

 to lSo°, the east longitude to be plus, and the west longi- 

 tude minus, in this particular departing from the recom- 

 mendation of the Roman Conference. The Washington 

 Conference also disagreed with the resolution of the 

 Roman Conference in regard to universal time, declaring 

 the universal day to be the mean solar day to commence 

 for all the world at the moment of mean midnight of the 

 initial meridian, coinciding with the beginning of the 

 civil day, and to be counted from oh. up to 24I1., a propo- 

 sition which, as already mentioned, had been debated at 

 the Roman Conference. Protocols were approved which 

 will be made the basis of an international convention 

 fixing Greenwich as the prime meridian. 



Practically, therefore, the recommendations are : — 



(1) That the prime meridian be that of Greenwich. 



(2) That longitude be counted from this meridian in 

 two directions up to 180 , calling east longitude plus and 

 west longitude minus. 



(3) That the universal day be the Greenwich civil day, 

 commencing at midnight and reckoning from oh. up to 

 24I1. 



After full discussion at two Conferences we may believe 

 that, regarding scientific requirements on the one hand 

 and practical considerations on the other, the conclusions 

 arrived at are the best which, under the circumstances, 

 were possible. We may now proceed to consider in 

 various ways their practical bearing. 



First, as affecting matters nautical and geographical. 

 By the adoption of Greenwich as the prime meridian 

 (which, if that of any one place were to be selected, was 

 clearly from its extensive use the one which had by far 

 the strongest claim to consideration), and by the reten- 

 tion of the system of counting longitude east and west 

 up to 1S0 , all British maps and charts (already exten- 

 sively used by most other nations) and all tables of 

 longitude as hitherto prepared remain still in harmony 

 with the recommendations of the Washington Conference. 

 And since foreign nations thus so largely use charts which 

 refer to Greenwich, the use of this meridian is likely in 

 time to become universal. This being so, some labour 

 of calculation might also be saved, for, considering that 

 large portions of the existing astronomical and nautical 



