222 



NATURE 



[May II, 1916 



towards which the upper end points. If, however, it 

 is vertical, and near the zenith, there is great danger. 

 If its altitude is, for example, a mile, a bomb dropped 

 would occupy 18 seconds in falling, if there were no 

 air. Owing to the resistance of the latter, this time 

 is greatly increased. It is only necessary to run at 

 right angles to the apparent direction of the Zeppelin 

 to be safe, even if one does not start until the bomb 

 is dropped. This rule may be tested by standing 

 under a telephone wire, which may be regarded as 

 representing the path of the Zeppelin. A plumb-line 

 will cover the wire only if the observer is. exactly 

 under the wire. No allowance is here made for the 

 wind, which always carries the Zeppelin to 

 leeward. It may be better, therefore, to 

 stand so that the Zeppelin is partially covered 

 by the edge of a house, a flagpole, or other 

 vertical line. There is no danger unless the Zeppelin 

 appears to ascend the line, remaining partially covered 

 as it approaches the zenith. The same principles 

 apply to aeroplanes. At sea, the vessel should take 

 a course at right angles to the direction from which 

 "the Zeppelin comes. Of course, these methods are 

 useless if the Zeppelin cannot be seen owing to clouds 

 or darkness, unless it is picked up by a searchlight. 



E. C. Pickering. 

 April 10. 



DAYLIGHT AND DARKNESS. 



THE House of Commons adopted on Monday 

 a resolution moved by Sir Henry Norman : 

 "That, in view especially of the economy in fuel 

 and its transport that would be effected by 

 shortening the hours of artificial lighting, this 

 House would welcome a measure for the advance- 

 ment of clock time by one hour during the 

 summer months of this year." The daylight 

 saving scheme put forward by the late Mr. W. 

 Willett in 1907 has, therefore, now been approved 

 by Parliament, and it is proposed to effect the 

 change of time during the night of Saturday- 

 Sunday, May 20-21. The normal Greenwich time 

 is to be restored during the night of Saturday- 

 Sunday, September 30-October i. In supporting 

 the motion on behalf of the Government, the Home 

 Secretary, Mr. Herbert Samuel, said it was 

 thought that the change could be effected without 

 legislation by Order in Council, " since this is only 

 a war measure adopted for war purposes." On 

 account, however, of the existence of an Act 

 which defines "hour " in any statute as Greenwich 

 mean time in Great Britain, and Dublin mean 

 time in Ireland, and also because, in conformity 

 with this Act, there are fixed the hours in factories 

 and workshops in which women and children are 

 employed, while a number of other establishments, 

 including licensed houses, are compelled by law to 

 keep certain times, the law must be altered in 

 order that the new time should have legal validity. 

 A Bill is, therefore, necessary, and it was intro- 

 duced in the House of Commons on Tuesday. 

 There is little doubt that the measure will pass, 

 and that from May 21 to October i the legal time 

 will be that of Mid-Europe instead of Greenwich 

 mean time. 



The time of sunrise in London on Sunday, May 

 21, is given in the calendars as 4.2, but by the 

 clocks it will be 5.2 ; and similarly, though the sun 

 NO. 2428, VOL. 97] 



will set at 7.50, we shall call the hour 8.50. The 

 actual time of morning high-water at London 

 Bridge will be 4.12, but the clocks on shore will 

 indicate 5.12; and there will be a like difference 

 between tidal times and public times all around 

 the coast. It will be no longer possible to speak 

 of, say, a two o'clock tide to a navigator at a 

 port, for this must mean Greenwich time to him, 

 as tidal tables have to remain unaltered, whereas 

 his two o'clock will be the landsman's three 

 o'clock. For a large part of the population there 

 will be two legal times from May 2 1 to October i , 

 and we shall be surprised if this confusion does 

 not lead to serious mistakes and accidents. 



All orders referring to lighting-up times, 

 closing of parks and other places at dusk, bur- 

 glary as distinct from larceny, and like matters 

 determined by solar time, will need adjustment; 

 in fact, Parliament has now to define legal time 

 afresh. Lighting-up times will, we suppose, 

 continue to be based upon Greenwich times, with 

 the necessary differences for latitude and longi- 

 tude, for they obviously cannot be determined by 

 the meridian of Mid-Europe. On May 21, for 

 example, the lighting-up time in London is 8.50, 

 and at Liverpool 9. 11, but in all cases an hour will 

 have to be added to give the clock times of light- 

 ing-up. Here, again, the double standard of time- 

 reckoning — one in calendars and tables, and 

 another in daily use — will be most confusing. 



The claims as to the great saving of expendi- 

 ture on fuel for illumination to be effected by the 

 daylight saving measure are, we believe, largely 

 over-stated. For two months from the end of 

 this month there will be no need for artificial 

 lighting until 9 p.m. or later in any part of the 

 British Isles ; and in such places as Newcastle and 

 Glasgow the lighting-up times will be nearer 

 10 p.m. than 9 p.m. during most of this period. 

 Men of science, like other citizens, recognise the 

 cheapness of using daylight; what they object to 

 is the alteration of clocks, instead of alteration of 

 habits, to induce reasonable use of daylight hours. 

 Whatever time is indicated by the clocks, most 

 people will not retire until an hour or two after 

 the sun has gone and they have used artificial 

 illumination for indoor rest or recreation. Though 

 the clocks will indicate 10.30 when daylight 

 occupations must end during June and July, we 

 doubt greatly whether there will be much reduc- 

 tion of the habitual interval between the close of 

 the outdoor life and the time of retiring. 



The daylight saving principle is, in fact, un- 

 necessary for at least half the period during which 

 it is to be in force; and over a large part of the 

 British Isles the hours of actual darkness are 

 then so few that the amount of artificial illumina- 

 tion used cannot be greatly reduced by advancing 

 clocks by one hour. Mr. Willett arrived at the 

 154 additional hours of daylight which his scheme 

 was to give the country by reckoning an extra hour 

 for each of the 154 days from April 15 to 

 September 15, and our legislators, journalists, 

 ' and commercial men base their conclusions as to 

 j the saving of fuel and light upon this estimate, 

 which they apply to the whole country. If we 



