KM URL 



[February 27. 1919 



bine working in series. Thi hjgh-pressun turbirn 

 the impulse type, and coupled l>\ mean 

 rte couplings and pinion to the starboard first 

 ii,,ii u In, 1. rhe low-pressure turbine is of thi 

 •11 type, and coupled in a similar manni 

 the port first reduction wheel. The first reduction 

 wheels are mounted on pinion shafts working into thi 

 second reduction wheel, which is connected direct ti 

 the thrust shaft with a thrust block ol the pivoted 

 type. The total shall horse-powei of the installation is 

 2900; the speed of the propellei is 78 revolutions per 

 minute, and each turbine has a -peed of 3500 revolu- 

 tions per minute. The gearing is arranged to givi 

 the following ratios: — From turbines to first reduction 

 wheel, 7-9 to 1 ; from firsl reduction gearing to second 

 reduction wheel, 57 to 1 ; and thi total reduction ratio 

 is 45 to I. I'lie wheel- and pinions are of the usual 

 double-helical type; the first reduction wheel- an 

 made of cast-iron with wrought-steel tyres shrunk on; 

 the second reduction wheels are of cast-iron with ca 

 steel tyres shrunk on; all four pinions are of nickel 

 steel. The axial pitches of the teeth in the first and 

 second reduction gearing are 7/12 in. and 1 in. respei 

 tiveh ; 'he angle of helix is 30°. 



The January, 1919, issue of the quarterly classified 

 lisl oi second-hand instruments for sale or hire pub- 

 lished b\ Mr. C. Baker, --44 High Holborn, W.C.i, 

 has been received. Several new pieces of apparatus, 

 which Mr. Baker can still supply, are included in thi 

 list and are -uitabb distinguished- Readers who ma\ 

 require microscopes, survey ing instruments, telescopi 

 spectroscopic apparatus, or physical apparatus of a 

 general bind should examine this comprehensivi 

 catalogue. 



OUR ASTRONOMICAL COLUMN. 



Comets. — M. Fayel lias calculated the following 

 extended ephemeris of Borrelly's comet for Greenwich 

 midnight; it should be observable with powerful in-tiu 

 ments for two or three months: — 



R.A. N. Dec!. Log r Log J, 



h. in. s. 



March 2 7 9 33 63 56 



6 7 17 51 63 17 0-26418 j 5 7 



10 7 26 25 62 34 



14 7 35 '3 6l 49 0-27717 0-13347 



18 7 44 7 61 1 



22 7 S3 3 6° 10 0-28939 0-16706 



26 8 1 59 59 17 



30 8 10 54 58 22 0-30146 0-19918 

 April 3 8 tq 46 57 26 



7 S 28 31 56 28 0-3I333 O ' ''IM. 



11 8 37 11 55 28 



15 8 45 42 54 28 0-32496 0-25932 



19 8 54 6 53 26 



23 9 2 21 52 24 0-33635 11 28748 



27 Q IO 29 51 21 



1 9 18 29 50 iS 0-34748 031443 

 5 9 26 22 49 14 



-,4 4 48 10 0-35834 0-34020 



Lick Observatory Bulletin No. 320 contains an 

 itical mi''. 1 .unlet 1 9 1 Srf (Schorr) calculated b\ 

 Mr. H. M. Jeffers from observations mi November 25 

 and December 3 and 7, 1918 : — 



T = l9i8 Oct. 16-442 G.M.T. 

 oi .85 37' o"1 

 &=IlS ',: (8' .918-0 

 * = 



<t> = 25 3 

 log a =0-512136 

 fi =605-066 

 Period= 5-8641 ye; 



NO. 2574, VOL. 102] 



I b. linn ui perihelion is decidedly lati period 



than in the Copenhagen orbit. 



"Annua rui Bureai des Lo gj l'des. — This 



must us, tui little annual is s. i widely known that it is 

 unnecessary to givi an account of its main features. 

 The essays vary from Mar to year; those in the 

 it volume are: (1) The figure- of relative equili- 

 brium of a rotating homogeneous liquid, bj P. topell 1 , 



and (2) The determination by interference of the 

 diameters of heavenh bodies, by Maurice Hamv. 

 in Treats the subject from an historical point of view. 

 In ginning with MacLaurin's ellipsoids of revolution, 

 gning on In those of Jacobi, with three unequal axes, 

 then the tracing of the connection between these two 

 1 lasses and the investigation of the points of bifurca- 

 tion; this leads on to the alternati direction of possible 

 bifurcation, namely, the pear-shaped figures investigated 

 b\ Liapounoff and Poincare, mam of which are illus- 

 ted in the text. Finally, the qui -ability 



is dealt with, and the remarkable propert) of its inter- 

 change from one das- of figure- to another at the 

 points of bifurcation. There is a very full biblio- 

 graphy. (2) Shows how the real diameters of such 

 bodies as satellites and minor planets may be inferred 

 from a study of tin ir interferenci fringes. The fol- 

 lowing determinations (reduced to distance unity) are 

 given as specimens: — lo, 400"; Europa, 4-35"; Gany- 

 mede, 640"; Callisto, 6-55*; and Yesla. 054". or 250 

 miles. The author considers thai with thi Mount 

 Wilson Too-in. reflector it might be possible bo deter- 

 mine the angular diameters of i-t magnitude stars. 



THE CHEMICAL DETECTION OF STRAIN 

 IN IRON AND STEEL. 



THE ninth volume of the Carnegie Scholarship 

 Memoirs of the Iron and Steel Institute con- 

 tains an account of an investigation on the above 

 subject by Messrs. Whiteley and Hallimond, of the 

 South Durham Steel and Iron Co. The 

 arose out of an observation made in tin- course of 

 experiments in connection with the Eggertz test for 

 combined carbon made by one of the authors. On 

 examining the composition of the gases evolved when 

 samples of steel were dissolved in dilute nitric acid, 

 the authors noticed that the nitrous gases given off 

 differed considerably in their proportions in the case 

 of different samples. They were at first inclined to 

 think that these variations were due to the influence 

 of other elements, such as carbon and phosphorus, 

 which are alwavs present in steels. Later work, how- 

 ever, showed that the chief cause of the variations 

 was the particular mechanical treatment to which 

 the different sample- have been subjected. 



The paper is divided into two parts In the first 

 the author- discuss in some detail the chemical 

 reactions involved, and the analyses ol tin gases 

 formed when iron is dissolved in nitric acid. In the 

 second they describe the changes in the reaction pro- 

 duced b] mechanical work on various iron and steel 

 samples, and show how tin effect can be used 

 to measure the progressive removal ol col.l work on 

 annealing. 



The reaction between nitric acid and various metals 

 has been the subject of numerous in/vesti 

 among which max he mentioned those ol \ efcw, 

 Divers, Mont, martini, and Stansbie. These n - 

 deal mainlv with copper, while iron has received much 

 less attention. The authors point out that .1 variety 

 of reduction product- i- obtained by the solution ot 

 u nitric acid. Nitrogen peroxide, nitric ami 

 nitrous oxide.-, nitrogen, ammonia, hydroxylamine, 

 m- have all b -1 in pro- 



