NJi TURE 



[February 3, 1910 



five years ago, the consumer of gas for power or heating 

 purposes has now to burn about 1200 cubic feet of gas in 

 the place of 1000, costing 3s. 2\A. as against 35., plus a 

 meter rental (varying with the consumption), plus the 

 extra cost of repairs caused by the additional sulphur 

 present. The consumer, for lighting purposes, if using 

 throughout an incandescent mantle, is not seriously pre- 

 judiced; if, however, he retains the batswing burner, his 

 outlay for the same amount of light has increased in the 

 ratio of about 4/3, plus a meter rental and plus an 

 increased cost of internal decoration due to the condensa- 

 tion on the walls and ceilings of an increased amount of 

 sulphuric acid. 



The Scientific American for January 15 shows an illus- 

 tration of the McClean-Lissaclc automatic rapid-fire gun, 

 which was tested last year by the Ordnance Department 

 of the United States Army. This gun is designed for 

 attacking balloons, and is mounted on a Packard 3-ton 

 automobile truck. The gun fired 3-lb. shots at the rate 

 of 100 per minute, the range being 35 miles. With bralces 

 on, the truck did not move on firing, and no shock was 

 perceived by those standing on the truck platform. With 

 brakes released there was a slight movement on the recoil, 

 but no shock. Further tests with this gun are being made 

 at Sandy Hook and Springfield for the army, and at Indian 

 Head for the navy. The same article also illustrates two 

 German automobile guns designed for the same purpose. 

 One of these is mounted on an armoured truck of 60 horse- 

 power, capable of a speed of 45 kilometres per hour. The 

 shell from this gun has a maximum height of trajectory of 

 3800 metres. 



The ninth report to the alloys research committee was 

 presented by Dr. W. Rosenhain and Mr. F. C. A. H. 

 Lantsberry at the meeting of the Institution of Mechanical 

 Engineers on Friday, January 21. Dr. Rosenhain ex- 

 plained that this report dealt with the properties of some 

 alloys of copper, aluminium, and manganese, and is con- 

 Sned to some of the more interesting alloys likely to be 

 of practical service. The greater part of the work w^as 

 confined to alloys containing less than 11 per cent, of 

 aluminium, and also less than 11 per cent, of manganese. 

 It is impossible to state adequately and briefly the enormous 

 amount of valuable information resulting from this research 

 — the report occupies 174 pages of the institution's trans- 

 actions. Specific mention might be made of the great 

 tensile strength exhibited by one of the alloys in the form 

 of a cold-drawn bar, having a yield point of 4088 tons 

 per square inch and an ultimate stress of 5208 tons per 

 square inch. This alloy had 999 per cent, aluminium, 

 201 per cent, manganese, and 88 per cent, copper. 

 Another alloy shows hardness sufficient to enable it to take 

 a cutting edge that will sharpen a lead pencil. In addition 

 to the mechanical tests and microscopic and freezing-point 

 investigations, corrosion in sea water has been examined. 

 Further and more searching tests on the latter are now 

 proceeding at Portsmouth Harbour, and have also been 

 arranged for in the warmer sea water at Malta Dockyard. 



The January number of the Journal of the Royal 

 Statistical Society begins a new series of the journal, to 

 be issued monthly during the session. It is hoped that 

 the greater rapidity of publication thus secured will be of 

 service, as papers read one month will now be in the hands 

 of fellows, and the public generally, by the middle of 

 the following month instead of sometimes not appearing 

 for three months or more, as is necessarily the case with 

 a quarterly journal. Current notes also form a new 

 section of the journal which it is hoped will increase its 

 general interest. 



NO. 2IOI, VOL. 82] 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrencbs in February: — 

 Feb. 4. 5h. Venus in perihelion. 



6. I2h. Meicuiy stationary. 



7. I2h. 25m. Uranus in conjunction with the Moon 



(Uranus 3' 19' N). 

 9. I2h. 36in. Vtnu^ in conjunction with the Moon 

 (Venus 13" 34' N.). 



12. oh. Venus in in'erior conjimction with the Sun. 



13. 13h. 22m. Saturn in conjunction with the Moon 



(Saturn l" 18' N.). 

 15. 6h. 12m. Mus in conjunction with the Moon 



(Mars 3^ I' N.). 

 19. I7h. Mercury at greatest elongation west of the 



Sun. 

 19. 2ih. 35m. Neptune in conjunction with the Moon 



(Neptune 4° 10' S. ). 

 26. 3h. Venus at greatest heliocentric latitude north. 

 ,, I7h. 34m. Jupiter in conjunciion with the Moon 



(Jupiter 2° 29' S.). 

 Mars. — Readers of these columns should be fairly well 

 acquainted with Prof. Lowell's views concerning the 

 Martian features and their significance, but they will find 

 interesting the comprehensive summary given by Prof. 

 Lowell in No. 13 of Scientia, the international science 

 review published at Bologna, and obtainable from Messrs. 

 Williams and Norgate. Therein the author reviews the 

 observations of the melting snow'-caps, of the " canals " 

 and oases, which, by virtue of their dependent vegetation, 

 undergo striking changes in conformity with the Martian 

 seasons, and the theoretical considerations which have led 

 him to conclude that Mars is habitable by organisms not 

 essentially different from those with which we arc 

 acquainted. That Mars has no water except that contained 

 in its atmosphere and that which forms the snow-caps, 

 Prof. Lowell avers, but he contends that that water is 

 artificially " engineered " in such a way that organic 

 existence is rendered possible. 



Caroline Hekschel and Her Comet Seeker. — At the 

 present moment, with the subject of comets so much !o 

 the fore, an article which appears in the January number 

 of Himmel und Erde is of especial interest. The writer 

 gives many details of Caroline Herschel's strenuous life 

 and describes her labours wdth the comet seeker. .'\ 

 facsimile reproduction of a letter, dated .August 5, 1S31, 

 from her to Director Hausmann, tells how the comet 

 seeker was made and how she wished it to be used after 

 she had finished with it. The instrument was made of 

 odds and ends by her brother " between breakfast and 

 dinner." "The tube had once been used as a Newtonian 

 finder to the 20-foot reflector. The circular board oncp 

 served for a fly-wheel in some experiment ; and for tbr 

 pole, I was sent to the scullery to find a mopstic. The 

 rest w^as sawed and chopped in the shapes as they were 

 wanted — as for plaining we could do without, there was 

 no time for niceties." Yet, she adds, it stood for forty- 

 seven years without wanting a single repair, travelling all 

 over the house and garden, at Slough, many a night ; and 

 with it she discovered five of the eight comets credited to 

 her name. 



EDDY FORMATION IN THE WAKE OF 

 PROJECTING OBSTACLES. 



r^ ONSIDER a stream bounded by and moving parallel 

 ^^ to the plane OX, with velocity U, and containing a 

 stationary vortex at A (a, b), or, what is the saine thing, 

 an unbounded fluid containing a stationary vortcx-pair at 

 .'\, B (Fig. 1). With the notation w=<l>+ii, z = x+iy, 

 (^=velocity potential, il' = stream function, the potential 

 function is given, for this case, by 



; U I : + 216 log ■ 



-a- /A 

 - a + iij 



Inside a certain surface OQP, the stream lines are closed 

 curves and the motion is cyclic ; outside, the fluid streams 

 past the surface as if it were a solid obstacle, as is well 



