1 64 



NATURE 



[September 29, 1921 



Sir W. G. Armstrong, Whitworth and Co., Ltd., 

 and has twin screws driven by Armstrong-Sulzer 

 Diesel engines. These engines are the largest en- 

 gines' of the type which have, up to the present, 

 been fitted in a British mercantile vessel. The vessel 

 has been constructed on the Isherwood longitudinal 

 system, and is 370 ft. long; the gross tonnage is 

 4550, and the mean draught is 24 ft. 3 in. with 

 6500 tons dead-weight on board ; under these condi- 

 tions the speed is 115 knots. Each engine has four 

 cylinders, 600 mm. bore and 900 mm. stroke, and 

 develops 1250 brake-horse-power at 100 revs, per min. 

 Durirtg the trials the fuel consumption of the main 

 engines was 0421 lb. per brake-horse-power per 

 hour. The pistons are cooled by the Sulzer spray 

 system, in which a spray of sea-water plays inside 

 the piston and is discharged against its inner walls. 

 The system works under atmospheric pressure with an 

 open discharge, so that the engineer can gauge the 

 itemperature of each piston and cylinder unit. 



A PARTNERSHIP is announced between Sir Charles 

 Bright, Mr. A. Hugh Seabrook (late chief engineer 



and general manager to the St. Marylebone, London, 

 and other electric supply undertakings), Mr. A. J, 

 Stubbs (late Assistant Engineer-in-Chief, H.M. Post 

 Office), and Lt.-Col. H. W. Woodall (director and con- 

 sulting engineer of gas and water companies) under 

 the style of Sir Charles Bright and Partners, consult- 

 ing engineers,, with offices at 146 Bishopsgate, E.C.2. 

 The estabUshment of this firm is of scientific interest 

 on account of the unusual combination of experts 

 represented by it, which marks a development of the 

 co-operation of gas and electricity. In addition to 

 advising upon the installation and operation of tele- 

 graphs, telephones, and wireless and electrical under- 

 takings generally, the firm may be consulted upon 

 gas, water, and colliery engineering. In view of the 

 heavy cost of fuel, economies have to be studied to-day 

 that were negligible before the war. The firm is 

 specialising in fuel conservation in relation to the 

 design and construction of power plants — steam, gas, 

 electric, hydro-electric, and oil — and particular atten- 

 tion is being devoted to the utilisation of low-grade 

 fuels and carbonaceous materials hitherto regarded as 

 waste products. 



Our Astronomical Column. 



Conjunction of Venus and Mars. — Mr. W. F. 

 Denning writes: — "A very interesting and close 

 approach of Venus and Mars may be well observed 

 in the morning sky of October 3 if the weather 

 is clear. The time of conjunction is at about 11 a.m., 

 -when the two planets will be separated by a space of 

 a little more than a third of a degree. 



''The best time to observe the event will be at about 

 4 or 5 a.m., as the sun rises a few minutes after 

 6 a.m. Venus will appear by far the. more brilliant 

 ■orb of the pair, and its strong silvery light will make 

 the red aspect of Mars feeble and insignificant. This 

 occasion will afford a good opportunity to make com- 

 parative observations of this sort, but neither of the 

 planets will be shining at its best ; in fact. Mars will 

 be at so great a distance from the earth that its bright- 

 ness will scarcely exceed that of a second magnitude 

 star. 



■'The two planets will be situated in the constella- 

 tion Leo, and about 10° east of Regulus, the most 

 conspicuous star in that constellation." 



Observations of Star Colours. — The Vatican Ob- 

 servatory has just published four volumes dealing with 

 ■observations of star colours on Schmidt's numerical 

 scale (modified by Osthoff). Three of the volumes are 

 separate catalogues, based respectively on the obser- 

 vations of Benedetto Sestini, S.J., at Rome (1844-46), 

 with revision by J. G. Hagen, S.J., of Friedrich 

 Kriiger at Aarhus, and of Heinrich Osthoff at 

 Cologne. The fourth is an index catalogue, com- 

 bining the results of the first three, and adding the 

 Harvard magnitudes and spectral types. The colours, 

 on the whole, follow the spectral types fairly closely ; 

 there is, however, a physiological effect, discussed 

 bv H. Osthoff, according to which a bright star is 

 estimated as whiter than a faint star of the same 

 tint; he investigated this by observing bright stars 

 with sectors of various angles over the object glass, 

 and found that it averaged 03 colour-unit per magni- 

 tude. Owing to this effect, the photographic deter- 

 mination of colour-index has advantages over the 

 optical method. 



NO. 2709, VOL. 108] 



The following are the adopted colour-numbers for 

 some bright stars : — Aldebaran, 6-3 ; Capella, 33 ; 

 Betelgeuse, 65; Procyon, 27; Pollux, 44; Arcturus, 

 47; Vega, 1-3; Altair, 24. It is only among the 

 faint stars of type M& that numbers approaching 9 

 or 10 are found. 



The Motion of the Perihelion of Mercury. — This 

 question is now of special interest owing to the close 

 agreement between the value of 43" per century given 

 by Newcomb and the value 42-89" deduced from 

 Einstein's theory. Newcomb estimated the probable 

 error of his determination as 2" per century; but an 

 article by E. Grossmann in Astr. Nacli., No. 5115, re- 

 examines the obsen-ational evidence, reaching the ■ 

 conclusion that the actual range of uncertainty is 

 much greater. Newcomb based his result partly on 

 meridian observations and partly on transits across 

 the sun. The difficulties in obser\'ations of the latter 

 phenomena are well known, consisting partly in the 

 "Black Drop," and partly in the unsteady image 

 which the sun's heat often produces. There is the 

 further fact that the transits all take place at two 

 particular points in the orbit, and consequently are 

 incapable of determining the motion of the perihelion 

 by themselves; they merely lead to an equation be- 

 tween different secular motions. The meridian ob- 

 servations are also not very satisfactory. They lead 

 in the mean to a distance of Mercurv- from the sun 

 2" greater than that corresponding with its period of 

 revolution. Moreover, Herr Grossmann shows that 

 the observations before and after 1850 (about the time 

 when chronographic observation began) have large 

 systematic differences. He finally obtains 29" and 

 38" as the limiting values of the secular motion indi- 

 cated by the observations. It should, however, be 

 added that a recent series of observations made with 

 the travelling-wire micrometer of the Cape Transit- 

 Circle gave a value very close to that of Newcomb. 

 It may be pointed out that the quantity actually ob- 

 servable is the product of the motion of perihelion 

 by the eccentricity, which amounts to only 8" per 

 centurv'. 



