April 22, 1909] 



NATURE 



231 



Suppose we consider eight hours' sleep as the nornuil 

 amount to be taken out of the twenty-four hours of a 

 day, and that a reasonable hour to retire is ii p.m. The 

 dilierence between this hour and the time at which the 

 lamps of road vehicles have to be lighted will show the 

 interval during which work or recreation cannot be 

 carried on out of doors, assuming that the lighting-up 

 time is always one hour after sunset. In Scotland there 

 is suflicient light to work or play during a large part of 

 the summer months for a much longer period than one 

 hour after sunset, but for simplicity the rule for lighting- 

 up tinie may be applied to the whole of our islands. The 

 following table gives the interval between this time as 

 thus defined and ii p.m. Greenwich Time: — 



July 30 



2 25 



Aug. 30... 3 10 ... 3 10 ... 3 S 



55 



2 50 



An examination of this table shows that, taking the bed- 

 time hour as n p.m., daylight can be used within two 

 hours of this time during June in the lowest latitude of 

 the British Isles, and within about one hour of ii p.m. 

 at any place north of Edinburgh. If we consider 9.30 p.m. 

 a time at which people have worked long enough at 

 business or pleasure out of doors to desire rest or recrea- 

 tion indoors before retiring at 11 p.m., it will be seen 

 that the actual interval of darkness before 9.30 is small. 

 For instance, taking latitude 52°, which is a little north of 

 London, during May, there is one hour before 9.30 p.m. 

 during which artificial light may be necessary ; during 

 June, there are less than twenty minutes; during July, 

 about fifty minutes ; and during August, about one and a 

 half hours. If the latitude of Edinburgh (56°) be con- 

 sidered, then at 9.30 p.m. there is no darl^ness during 

 May and June; in July people give up outdoor occupations 

 needing daylight about half an hour before 9.30 p.m., and 

 in .\ugust about one and a half hours before that time. 

 In higher latitudes the people can play or work out of 

 doors up to 9.30 p.m. or longer during the whole of 

 May, June, and July. The only argument that can be 

 derived from latitude is that North Britain should be 

 excluded from the provisions of the Bill. 



Now as to the zone or international system of time- 

 reckoning. In the days when places were not within easy 

 communication with one another, either by rail or telegraph, 

 local time was commonlv used. The necessity for a uniform 

 standard became clearly evident when railway time-tables 

 had to be printed. W'e have now become so used to this 

 single system of time-reckoning that few of us remember 

 that formerly it was common to see the announcement of 

 railway companies, " London (Greenwich) Time observed at 

 all stations." By the introduction of standard time, order 

 was called out of chaos, though it meant that for places 

 west of the Greenwich meridian time indicated bv the sun 

 is after the time indicated by clocks. A still further advance 

 w^as made when the Greenwich meridian was adopted as the 

 prime meridian for the international system of time- 

 reckoning. 



Thanks chiefly to the persistent advocacy of Sir Sandford 

 Fleming, twentv-four standard meridians are now recog- 

 nised, beginning with Greenwich, and counting toward the 

 east. The time of each of these meridians is thus one hour 

 behind that of the next meridian to the east of it, and one 

 hour in advance of the next meridian to the west. Each 

 meridian may be regarded as the mid-line of a zone 15° of, 

 longitude in width, so that the twenty-four meridians give 

 the standard times on the international system for the 

 whole world. It is usual for places within half an hour of 

 the standard meridian to adopt the time of that meridian as 

 its mean time, but in some cases the line midway between 

 two consecutive meridians of the twenty-four hour system 

 is taken as the standard meridian. 



.As Sir Robert Ball has given his support to the Daylight 

 Saving Bill, it is of interest to notice what he says in his 



NO. 2060, VOL. 80] 



" Popular Guide to the Heavens " as to the value of uni- 

 formity and system in the reckoning of time. Describing- 

 standard time, he remarks : — " As soon as communication 

 by railway and telegraph is established in a country, it is- 

 convenient to adopt throughout the country a uniform 

 system of time. Very usually the time adopted has been at 

 first the mean time of the capital. But as communication 

 between different countries increases, great inconvenience 

 arises when allowance has to be made for a difference of 

 adopted time involving an odd number of minutes and' 

 seconds. K large number of countries and States have 

 therefore adopted a standard system of time based upon that 

 of Greenwich, and differing from it by an exact number of 

 hours, with occasionally an odd half-hour." 



The subjoined table, from " Whitaker's Almanack,' 

 shows the countries in which this system of standard time, 

 with the prime meridian at Greenwich, has been adopted : — • 



Central Fast or .Slow on 

 Country. Meridian. Greenwich Time 



Mid-Europe 15° E. ... ih. fast. 



East Europe, British S. Africa, Egypt 30° E. ... 2h. fast. 



Mauritius and Dependencies 60° E. ... 4h. fast. 



Chagos Archipelago 75° E. ... 5h. fast. 



India S2^°E. ... 5ih. fast. 



Calcutta 90° E. ... 6h. fast. 



Burma 97^° E. ... (sVn. fast- 

 Hong Kong, Borneo, West Australia 120" E. ... 8h. fast. 



Japan I35° E- .■■ 9li. fast. 



South Australia 142^° E. ... 9jh. fast. 



Victoria, New South Wales, Queens- 

 land, Tasmania 150° E. ... loh. fast. 



New Zealand 1724° E. ... iiih. fast. 



Iceland 15° W. ... ih. slow. 



Atlantic... 

 Eastern ... 

 Central ... 

 Mountain 

 Pacific ... 



60° W. ... 4h. slow. 



75° W. ... 5h. slow. 



90° W. ... 6h. slow. 



105° W. ... 7h. slow. 



120° W. ... Sh. slow. 



Greenwich Time is used in Spain, Belgium, Holland,. 

 Gibraltar, and Faroe (Sheep Islands). 



What the Daylight Saving Bill proposes, therefore, is that 

 from the third Sunday in April to the third Sunday in Sep- 

 tember we shall use the mid-Europe meridian as our 

 standard meridian, and the Greenwich meridian during the 

 rest of the year. It is only necessary to state this fact to- 

 show how the proposals of the Bill would introduce con- 

 fusion into what is now a simple and scientific system. If, 

 as is suggested, some other countries in various latitudes 

 may follow suit and change their standard meridians during 

 various months, the result would be absolute chaos insteacf 

 of scientific order. 



There is only one other point to which we can refer now ; 

 it relates to the portion of the year during which the pro- 

 visions of the Bill are to take effect. .As Mr. L. C. W. 

 Bonaclna pointed out in Nature of March 18, the divisiort- 

 is unscientific, and follows no natural order. 



The following table shows the days on which the sunV 

 declination is approximated the same. In any given lati- 

 tude thp duration of sunlight upon each day in any pair is^ 

 equal, that is to say the amount of daylight is the same. 



Sun's Declination Days of Equal Sunlight 



20° N. May 21 July 24 



15° ,, May I Aug. 13 



10° ,, April 16 Aug. 2S 



5° ,, April 3 Sept. 11 



0° ,, March 21 Sept. 23 



The Bill proposes that the change of time shall be from 

 the third Sunday in -April to the third Sunday in September, 

 but it is evident that whereas the latter date is about the- 

 auturnnal equinox, the former is nearly a month after the 

 spring equinox. The declination of the sun in the third 

 week of .April is about 12° N., and the corresponding de. 

 clination after the summer solstice is about August 22. If, 

 therefore, the duration of daylight is intended to determine 

 the dates of change of time, these dates should be the thiid' 

 week in March and the third week in September, or th* 

 third week in -April and the third week in .August. 



