September 17, 1914] 



NATURE 



dge of conditions in the upper air will eventually 

 .i.row light upon the matter, (c) Effect of icebergs 

 in the Southern Ocean : From an examination of the 

 Meteorological Office tables of icebergs published in 

 the Monthly Meteorological Charts of the Indian 

 Ocean, separately tabulated for each ocean, by Dr. 

 Shaw's direction, it does not appear that the icebergs 

 of the Indian Ocean have any material effect. The 

 data for the South Atlantic appear to be more promis- 

 ing, but no definite conclusion can yet be formed. 



The Indian Association for the Cultivation of 

 Science has republished, as Bulletin No. lo, under the 

 title, " Optical Theories : a Brief Historical Survey," 

 the address delivered by Prof. Mallik at the annual 

 meeting in November last. In sixteen pages the 

 author sketches the development of scientific ideas 

 as to the nature of light from those of the early Greek 

 philosophers to the modern view, according to which 

 it is an electromagnetic phenomenon taking place in 

 an aether through which are distributed singularities 

 of a simple kind known as electrons and of a complex 

 kind known as matter. He shows that at the time 

 the Greeks were discussing the rival theories of 

 Pythagoras, that light consisted of particles projected 

 from luminous bodies to the eye, and of Empedocles, 

 who held that for vision a so-called "visual influence" 

 was necessary in addition, the Indian philosophers 

 ^^ ere discussing the problem on almost identical lines. 



In Mr. F. W. Lanchester's second article in 

 Engineering for September ii, on aircraft in warfare, 

 it is stated that the weaknesses of the dirigible on the 

 defensive are so great and of such a chtiracter as to 

 render it quite unfit to remain an active participant 

 n aerial warfare. It may escape for a time, and may 



nder a certain amount of useful service, but only 

 I hanks to the circumstance that the number of high- 

 powered, fast-climbing aeroplanes is comparatively 

 limited, and to the fact that scientific methods of 

 attack have not yet been fully worked out or put into 

 practice. However, even to-day the finest of Ger- 

 many's fleet of Zeppelins would be absolutely at the 

 mercy of a modern aeroplane in the hands of a man 

 prepared to make his one and last sacrifice. So 

 fragile and combustible a contrivance as a dirigible, 

 whether rigid or non-rigid, can never, in Mr. Lan- 

 chester's opinion, survive in the face of the rapid 

 development of the modern aeroplane and the engines 

 of offence with which before long it will be furnished. 



Some interesting notes on the relation of rainfall 

 and yield are contributed by Mr. D. Halton Thomson 

 to Engineering for September 4. If the annual yield 

 for a given drainage area be plotted against the rain- 

 fall for the corresponding period, the points generally 

 are distributed in a haphazard manner, and there is 

 difliculty in drawing a simple curve — usually assumed 

 to be a straight line. The irregularities may be due 

 to inaccurate obser\'ations, the varying physical con- 

 ditions of the drainage area from year to year, and to 

 the fact that the yield lags behind the rainfall. If 

 twenty or more consecutivt annual observations are 

 available, the author suggests that the two phenomena 

 may be correlated on the assumption that the rainfall 

 NO. 2342, VOL. 94] 



of a given frequency produces a yield of the same 

 frequenc}'. Time-lag and difference of time-distribu- 

 tion may be eliminated by this means. The author 

 derives a formula on this assumption for the Redmires 

 drainage area of the Sheffield Waterworks, and finds 



Y = R— 14, Y being the annual yield and R the annual 

 rainfall, both in inches. The formula for the Trench- 

 ford drainage area of the Torquay Waterworks is 



Y = o"9R— 13. In the first case the annual evapora- 

 tion is 14 in., whatever the rainfall, and in the second 

 case the annual evaporation increases slightly with 

 the rainfall. 



The Engineer for September 4 has an article dealing 

 with the problem of pitwood supplies, the dearth of 

 which, brought about by the war, is becoming a 

 matter for serious consideration by collier}- companies. 

 Northern Russia, whence important cargoes have been 

 usually shipped, is no longer able to keep up the 

 supply, and scarcity of labour in south-west France 

 has resulted in the suspension of cutting and trans- 

 porting ; shipments from Norway and Sweden are at 

 present impracticable. It seems that only one alter- 

 native is to be found if the dearth of pitwood becomes 

 extreme. To most collieries the permanent use of 

 steel would be too expensive. It has been suggested 

 that scrap tubes and rails, cut to suitable leng^s, 

 would make good substitutes for pit timber. A mid- 

 land collier)' has used for some time props made from 

 old steel pipes; these are filled with soft and hard 

 wood, the pipes forming a strengthener to the wood 

 portion. This composite prop is lighter and stronger 

 than the ordinarj' wood prop, is adjustable in length, 

 and by its soft ends gives good warning of a collapse. 

 Our contemporary suggests that the filling in of 

 worked out parts of mines with sand, ash, slag, etc., 

 would lead, among other important advantages, to a 

 diminished demand for timber for pit purposes. 



OUR ASTRONOMICAL COLUMN. 



Co-MET 1913/ (DELAV.\N).^Delavan's comet is gradu- 

 ally moving westward among the stars ; while it is 

 now best observed in the early morning, it will, 

 towards the end of the month, be an evening object for 

 observation as well. The ephemeris given in this 

 column last week is quite sufficient tor anyone to 

 detect this naked-eye object. Those possessing clock- 

 driven equatorials can do useful work by strapping 

 small cameras on to the telescope tube for the photo- 

 graphy of the tail. During the evening of September 

 14 the comet was seen to have brightened very con- 

 siderably, and was a conspicuous object to the naked 

 eye. It was situated towards the west of 6 Ursae 

 Majoris (32 mag.), but a mo-e correct position would 

 be to the west of 31 Ursae Majoris, and close to this 

 star. In fact, 31 Ursae Majoris was involved in the 

 tail. The nucleus closely approximated in brightness 

 to V Ursae Majoris, a fourth magnitude star. 



Further News of Ecupse Parties. — ^The current 

 number of the Observatory (September) publishes 

 several items of interest about the parties which went 

 out for the eclipse. It is stated that no news has 

 come to hand about the Cambridge Solar Physics 

 Observatory party, but that Mr. Stratton had been 

 p-eviously recalled for military service, and arrived in 

 England on August 23. Major Hills and Prof. Fowler 



