236 TRANSACTIONS OF THE [MAY 17, 



down the eastern coast of Africa from Aden to the Cape ; so that 

 now it is perfectly ])racticable, if it is desirable, to have one 

 standard of time in all the civilized world. 



A word perhaps is here in place as to this question of standard 

 time, and the beginning of the day. Tlie adoption by our rail- 

 roads of the system of standards differing from Greenwich time 

 only by entire hours has, I think, been admittedly a great ste]) 

 in advance, as regards public convenience and safety in trav- 

 elling. At a few points, where standard and local time happen 

 to differ by nearly the maximum possible amount of half an 

 hour, some annoyance is felt and there is still some opposition; 

 but it seems quite clear that, in this country at least, all resistance 

 will soon die out. 



As regards the more purely astronomical question of making 

 the astronomical day coincide with the civil day, by beginning at 

 midnigiit, instead of noon, as it does at present, there is more 

 difference of opinion. For my own part, I am frankly in favor 

 of the change, because I see no use in perpetuating an anomaly 

 which is sometimes annoying and confusing. At the same time 

 the change would, of course, involve some inconvenience to 

 computers and night-observers, and it must be admitted that 

 at present a large number, and )K)ssibly a majority, of the most 

 eminent astronomers, in other countries as well as in this, are op- 

 posed to it. Those of us whose work falls about as much in the 

 day as in the night, and those, I think, who take a long look 

 ahead, are in favor of the reform; but those whose work is mainly 

 nocturnal, or is based on observations made cliietly at or near the 

 "witching hour," dread the inconvenience of a change of date in 

 the midst of the record, and the risk of confusion in the interpre- 

 tation of old observations. 



The question, however, seems to me not a very important 

 one. 



I notice that the visitors of the Royal Observatory have just 

 recommended that the change be introduced into the British 

 Nautical Almanac for 1891. 



Before passing to the moon, a word should be added as to the 

 outcome of the most recent investigations regarding the steadi- 

 ness of the earth's rotation. Some irregularities in the lunar 

 motions have a]ipeared to justify a suspicion, at least, that they 

 might be caused by irregularities '\u the length of the day. The 

 researches of Nevvcomb upon ancient eclipses and occultationsof 

 stars give results not necessarily inconsistent witii this hypo- 

 thesis, periuvps even sliglitly in its favor; but his careful ex- 

 amination of the past transits of Mercury contra-indicates it 

 pretty decidedly. 



