i6o 



NATURE 



[October 23, 1919 



Some space is devoted to the importance of inventions 

 and research in connection with war munitions, and 

 it is interesting to note that Sir Robert's firm is now 

 in a position to manufacture a heavy calibre naval 

 shell which, for range and piercing power, will far 

 outstrip anything previously accomplished. Invention 

 should be stimulated and every effort made to discover 

 fresh inventors, and, once they are discovered, to 

 encourage them to give their ideas to the world "so 

 that everyone may benefit from them. 



Considerable interest is attached to the description 

 in Eifgineering for October lo of the geared turbines 

 supplied by the De Laval Steam 'lurbine Co. to 

 the Swedish destroyers Wrangei and Wachlmeister. 

 The high- and low-pressure turbines occupy separate 

 casings, and drive pinions tngaging on opposite sides 

 of the main gear wheel. The high-pressure turbine 

 casing accommodates a cruising element, and the low- 

 pressure turbine an astern turbine. The wheels of 

 both high- and low-pressure turbines are designed to 

 make 3600 revs, per min. at full power, and the 

 maximum peripheral speed is 180 metres per second. 

 The cruising element consists of one velocity- 

 compounded wheel, followed by a simple impulse wheel. 

 The main turbine has four wheels. The astern tur- 

 bine has one velocity-compounded wheel with two 

 rows of blading, followed by a simple impulse wheel. 

 The aggregate shaft horse -power at full power is 

 11,000, with the propellers running at 450; the astern 

 shaft horse -power is 4400, with propellers running at 

 250. With steam 97 per cent, dry, the turbines were 

 guaranteed to consume not more than 52 kg. of 

 steam per shaft horse-power hour at full load. Double 

 helical gear wheals are used for speed reduction, and 

 the pinions are rigidly mounted. The pitch line speed 

 at full power is 35 metres per second. Michel thrust- 

 blocks have been fitted, and their remarkable qualities 

 confirmed by the tests. 



OUR ASTRONOMICAL COLUMN. 



^OVM. — Yet another nova has been found on the 

 Harvard plates, this time by Miss Woods (Harvard 

 Bulletin 693). Position for 1875 : R.A. i8h. 24m. 6-23., 

 S. declination 29° 289'. Its former magnitude was 

 14, but it rose temporarily to 11 in 1901. On April 24, 

 19 19, it rose to 7, and has now sunk again to 12, its 

 image appearing nebulous. The magnitudes are 

 photographic. 



Pubs. Ast. Soc. Pac, .August, 1919, contains a 

 paper by Dr. Shapley on a nova of another kind that 

 was discovered by Prof. Wolf two years ago, and 

 independently by Prof. Barnard in the present year. 

 Its place for 19170 is R.A. i/h. 35m. 13-453., S. 

 declination 11° 53' 57-6"; its photographic magnitude 

 is II (Harvard scale); spectral type, FO ; radial velo- 

 city large and positive. All plates exposed before 1909 

 fail to show it; all since 1910 show it. Three inter- 

 pretations are suggested : — (i) That it is refally just 

 beginning its stellar career, in which case it is of 

 unique interest ; (2) that it is a long-period or ir- 

 regular variable, somewhat like t] Argijs ; and (3) that 

 it has just emerged from behind an obscuring nebula. 

 To test this last suggestion. Dr. Shapley took a long 

 exposure with the 60-in reflector and studied the dis- 

 tribution of faint stars. The results, given in the 

 paper, while not inconsistent with the hypothesis, give 

 no decisive evidence in its favour; there is no distinct 

 line of demarcation of stellar density, as in some of 

 Prof. Barnard's dark nebular regions. However, a 

 much smaller cloud than these would suffice in this 



NO. 2608, VOL. 104] 



Mr. Joy has made an estimate of the star's distance 

 by the Adams spectroscopic method, finding 500 par- 

 sees. A Harvard plate of 1909 July 9 shows it of 

 magnitude J4-4; 1910 March 21, 11-3. Since- 1915 It 

 has been 11. 



Both Mr. C. P. Olivier {Ast. Journ., No. 757) and 

 Messrs. Van Maanen and Sanford (Pubs. Ast. Soc. 

 Pac, August, 1919) publish preliminary values of the 

 parallax of Nova Aquilae 1918. Their values (absolute 

 parallax) are 0060" and 0009". The latter, which 

 implies a distance of 362 light-years, is close to the 

 values foimd for Nova Persei, both by direct measures 

 and by the expanding nebular illumination. All the 

 observers contemplate further measures when the 

 brightness of the nova has sunk nearly to that of the 

 comparison stars. 



The Sun-spot Cur'C'E. — Mr. Seth B. Nicholson gives 

 an interesting curve of sun-spot activity in Pubs. 

 Ast. Soc. Pac, August, 1919. It is constructed simply 

 from the number of spots, regardless of area. Mr. 

 Nicholson places the late maximum in September, 1917, 

 and the curve since then shows a notable decline. 

 The previous maximum is placed in May, 1905, and 

 is both flatter and lower than the recent one. The 

 minimum is shown in June, 1913. There are also 

 curves of the mean latitude of spots, which show tha: 

 the fall in latitude since the last minimum has been 

 much steeper than in the preceding cycle. 



Mr. Nicholson directs attention once more to the 

 resemblance of the spot-activity curve with the light- 

 curve of Cepheid variables. The sun's surface is cer- 

 tainly not pulsating, as those of the Cepheids are 

 believed to be; if the resemblance of curve means any- 

 thing, it suggests that there may still be remnants of 

 pulsation in the sun's interior. 



Solar Radiation.— Mr. C. G. Abbot (Proc. Nat. 

 .Acad. Sci., U.S.A., September, 1919) gives an account 

 of the simultaneous measures of solar radiation made 

 in 1918 at Mount Wilson and Calama, Chile. 'The 

 results give still stronger support to the hypothesis 

 that the short-period variations in the radiation are in 

 the sun itself than did those at Mount Wilson and 

 .Algeria in 1911-12. Mr. Abbot states that the Calama 

 results are telegraphed to Argentina, and successful 

 predictions of temperature are based upon them. He 

 suggests additional radiafion stations at various cloud- 

 less regions, which he anticipates would be of great 

 utility in weather prediction. 



11 



NEW SOURCES OF ALUMINIUM IN 

 NORWAY. 



■p^URING the war neutral as well as belligerent 

 •L^ countries had to search within their own 

 borders for those raw materials which formerly they 

 were content to import ; new occurrences of well- 

 known ores have been discovered, and new method.s 

 devised for winning important products from rocks 

 which hitherto have possessed no commercial value. 

 Norway was particularly hard hit by the curtailment 

 of international trade, and, amongst other problems, 

 that of finding a home source of aluminium pre- 

 sented itself, and seems to have received a promising 

 solution. 



The metal aluminium can be obtained by elec- 

 trolytic means from its oxide, and nearly all the 

 suggested methods of manufacture depend upon this 

 as a final stage, the main difficulty being the pre- 

 paration of a sufficiently pure oxide, free from iron 

 and silica. The ore commonly used is bauxite, after 

 a rather costly preliminary purification by the Baeyer 

 process. At the outbreak of war the Central Powers 



