'254 



NATURE 



[October 21, 1920 



illustrated, and Winkler's method for estimating the 

 volume of dissolved air in water explained. The 

 lecturer referred to the utility of this work in such 

 diverse fields as public health and oceanography, and 

 indicated the importance of dissolved air to sub- 

 aqueous plant and animal life. The function of sub- 

 merged green plants in absorbing carbon dioxide and 

 liberating oxygen was explained, and it was stated 

 that large quantities of oxygen in excess of saturation 

 were found after a period of plant activity in bright 

 light. One function of this dissolved oxygen is to 

 maintain a healthy condition in water by oxidising 

 submerged refuse — a process largely dependent upon 

 the presence of living organisms. Reference was also 

 made to geological changes due to dissolved carbon 

 dioxide, to hardness produced by the same gas, and 

 to the corrosive action of water containing dissolved 

 air as exemplified by the oxidation of ironwork in hot- 

 water radiators, and by the corrosion observed in all 

 steam-raising systems owing to the oxygen dissolved 

 in the feed-water. At the close of his lecture Mr. 

 Coste referred in eloquent terms to the work done at 

 Finsbury College during the past thirty-five years, and 

 deplored the fact that the closing of the college was 

 contemplated. 



Engineering for October 8 gives some interesting 

 particulars regarding fabricated ships constructed in 

 the United States. It will be remembered that these 

 ships were so arranged as to permit the separate parts 

 to be manufactured by a large number of firms and 

 then assembled at the shipyard. The fabricated 

 freighter has now been afloat long enough to experi- 

 ence sufficiently varied conditions to reveal its sea- 

 worthiness. It is a known fact that steamers of this 

 kind have been able to forge ahead in the teeth of 

 storms that have driven larger boats of the usual 

 build to leeward. Replacements in cases of break- 

 down or injury have been made very promptly. Two 

 steamers, one of which was a fabricated vessel, col- 

 lided, and each smashed a hawse-pipe ; the fabricated 

 vessel was repaired from stock in a few hours, whilst 

 repairs to the other ship took six weeks. Reports 

 made by masters and chief engineers reveal the sound- 

 ness of the hulls and their unusual tightness and 

 freedom from leakages in the cargo-bilges, etc. Up to 

 April I of the current year 120 fabricated craft had been 

 launched from the twenty-eight ways of the Newark 

 Bay shipyard, the keel of the first having been laid 

 in December, 1917 — a feat which constitutes a record. 

 It is proposed to carry on this yard, and the Sub- 

 marine Boat Corporation has taken it over from the 

 Government. The programme provides for extensive 

 developments of both the yard and its neighbour- 

 hood, with the idea of making that point a highly 

 equipped port of entry and dej5arture, with dry docks 

 and other repair conveniences. 



We learn that the X-ray and electro-medical busi- 

 ness of the High Tension Co. has been purchased by 

 X Rays, Ltd. Arrangements have also been made 

 whereby Mr. Mortimer A. Codd, the author of a well- 

 known book on the subject of high-tension apparatus, 

 becomes the director of research for X Rays, Ltd. 

 The direct association of an X-ray research laboratorv 

 NO. 2660, VOL. I06I 



with a manufacturing firm has yielded such astonishing 

 results in America that one may look with confidence 

 to the similar plan which has been initiated in this 

 country. 



We are informed that the head offices of Siemens 

 Brothers and Co., Ltd., and of Siemens Brothers 

 Dynamo Works, Ltd., will be removed shortly from 

 Palace Place Mansions, Kensington, London, W.8, to 

 Caxton House, Westminster, London, S.W.i. 



Our Astronomical Column. 



The Nova in Cyg.nus. — This object has continued 

 to decline in brilliancy at a fairly steady rate. Mr. 

 Denning writes that since the end of .August the star 

 has lost light at a rate equivalent to one-tenth of a 

 magnitude daily. The nova has exhibited features dif- 

 fering in several respects from those of the bright novae 

 of 1901 (Perseid) and 1918 (.\quilid), which showed 

 remarkable fluctuations in their declining stages and 

 presented phenomena analogous to those of ordinary 

 variable stars. It seems, in fact, as though the new 

 stars of 1901 and 1918, after their great outburst and 

 quick decline, were subject to a series of minor out- 

 bursts affecting them at short and fairly regular 

 intervals. 



No such disturbances have apparently been observed 

 in the case of Nova Cygni. At Bristol, during the 

 fifty-five nights from .August 20 to October 13 in- 

 clusive, the star was observable on forty-seven nights, 

 and it has now become a rather faint telescopic object, 

 its magnitude on October 7 being only SJ. 



It is remarkable that since 1848 twelve new stars 

 have been discovered which were visible to the naked 

 eye, although during the preceding 150 years not one 

 nova was recorded. 



Connection of Planetary Nebula with Helium 

 Stars. — Astr. Nach., No. 5065, has an article by Herr 

 H. Ludendorff on this subject. Herr Ludendorff alludes 

 to the puzzling fact that the planetary nebulae show a 

 high average velocity in the line of sight, while the 

 helium and Wolf-Rayet stars, with which they have 

 spectroscopic affinity, haye a conspicuously low one. 

 It was at first thought that the number of nebulae on 

 Keeler's list, which was twelve, might be insufficient 

 to deduce a trustworthy mean. But the publication 

 of a much larger list of ninety-six nebulae by Camp- 

 beJl and Moore has increased the mean radial velocity 

 from 25 to 30 km. /sec. It becomes verv difficult to 

 make any plausible scheme of cosmogony into which 

 these nebulcB will fit. The low radial velocity of the 

 helium stars is generally explained by their large mass 

 on the assumption that the law of equipartition of 

 energy applies to stellar velocities. There is, however, 

 evidence of considerable mass in the case of the 

 planetary nebula also. Campbell noted spectroscopic 

 evidence of rotation in several cases. Combining 

 these with van Maanen's parallaxes, Herr Ludendorff 

 finds values for the masses of four planetaries as 14, 

 19, 162, and 28, that of the sun being unity. In view 

 of this difficulty, he re-examines the evidence that 

 soectroscopic binary systems give of the masses of 

 the B stars, and states' that it appears that those with 

 the largest mass have also the largest radial velocity, 

 and that the same rule appears to hold for the Wolf. 

 Ravet stars. 



While this result may help to bridge the gulf 

 between the planetaries and kindred types of stars, 

 it only removes one difficulty to create another. It 

 remains to give a reason.able explanation of the 

 increase of velocity with mass, which is quite opposed 

 to preconceived ideas. 



