420 



NATURE 



[December 2- 



L 



1919 



OUR ASTRONOMICAL COLUMN. 



Barnard's Proper-Motion Star. — It was shown 

 in Mon. Not. for November, 1916, that this star was 

 observed by Lamont at Munich in 1842, being 

 Mun. (i) 15040. Further confirmation of this is given 

 by K. Graff in Ast. Nach. (4989 and 5007). He has 

 surveyed the region with the 6o-cm. refractor at 

 Bergedorf, and gives visual magnitudes on the Har- 

 vard scale, and colour on the Osthoff scale, of 

 twenty-eight stars in the region. The Barnard star 

 is of mag. 937 and colour 34, being the reddest star 

 in the field. There are nineteen individual measures 

 of its magnitude, ranging from 922 to 9-60, but they 

 are not grouped in a manner suggesting variability. 

 The magnitude of the star Mun. (2) 6966, which 

 Bauschinger observed in 1886 in an unsuccessful 

 search for Mun. (i) 15040, is 10-79 3"*^ colour 20. 

 Its proper motion is small, and it must have been 

 extremely near the Barnard star in 1843. As there 

 was some doubt whether the star B.D. +4° 3561 was 

 the Barnard star or Mun. (2) 6966, Prof. Kustner has 

 re-examined the original zones at Bonn, with the 

 following interesting result. Zone 462 was observed 

 on 1854 May 30, the air being very clear. The fol- 

 lowing two stars were recorded in the region : — 



Mag. 



K.A. iSss'o 



N. Decl. 1855-0 



(a) 

 (b) 



--- 95 17 50 43-8 +4 i6-5 



--- 95 17 SO 443 +4 i7-9 



Zone 472 was observed on 1854 July 24, the air again 



being clear ; on this night a single object was 



recorded in the place, thus : — 



(c) ... 93 17 50 41-9 -+-4 17-3 



In editing the B.D. it was assumed that objects (a) 

 and (c) were the same, and their mean was taken as 

 the position of -1-4° 3561, while object (b) was omitted 

 as insufficiently observed. However, making use of 

 our later knowledge, it is fairlv certain that (a) is 

 Mun. (2) 6966, (b) is the Barnard star, while (c) is 

 probably the two objects observed as one (the tele- 

 scope was small and the magnifying power low). 

 This would account for the greater brightness recorded 

 on July 24, which is unquestionably too high for 

 Mun. {2) 6966. In view of these facts, the two stars 

 must divide the claim to the title B.D. +4° 3561, but 

 another early observation of the Barnard star (1854 

 May 30) has been established with tolerable certaintv. 



Mr. Graff estimates the diameter of the Barnard 

 star as 1/20 of the sun's, or half that of Jupiter. 

 This is based on its absolute magnitude arid an esti- 

 mate of its surface brightness from the character of 

 the spectrum. It seems, however, unlikely that so 

 small a body could ever attain the temperature neces- 

 sary for a sun-like state. Prof. Eddington considered 

 that a mass 1/8 of the sun was the minimum for the 

 attaining of a sun-like condition. If we assume a 

 density eight times the sun's, or twice that of the 

 earth, this would give a diameter 1/4 of the sun's. It 

 seems unlikelv that the actual value is less than this. 



The Gre.at Solar Prominence of Last May. — 

 Several reproductions of the photographs of this 

 object, taken by the eclipse expeditions, have recently 

 appeared (Observatory, November, and the British 

 .Astronomical .Association's Journal, October). The 

 Monthlv Notices for June contained some photographs 

 taken with the Cambridge spectroheliograph. The 

 Astrophvsical Journal for October gives some beauti- 

 ful photographs taken at short intervals with the 

 Yerkes 40-in. refractor. The first photograph was 

 taken at ih. 17m. G.M.T., about midway between 

 the Sobral and Principe pictures. The prominence 

 then formed a ereat arch, extending from -42° to +6" 



NO. 2617, VOL. 104] 



in latitude, and 45' high. It was rising rapidly, and 

 ijh. later it had broken away from its terminal 

 columns. Successive plates show that the rising con- 

 tinued steadily, and at 7h. 57m. G.M.T. its height 

 was 17', or more than a solar radius. It rose from 

 200,000 km. to 760,000 km. in 6h. 40m. Mr. Ever- 

 shed also secured many photographs of the object at 

 Kodaikanal, but the longitude of Yerkes was more 

 favourable for securing its most dramatic stage. The 

 prominence had been in existence since March, but on 

 the eclipse day it suddenly changed from the quiescent 

 to the eruptive type. The Yerkes observers direct 

 attention to a claw-like marking at the base of one 

 of the columns, from which they infer that this base 

 was exactly on the sun's limb. 



ATOMIC DISINTEGRATION AND HEAT 

 ENERGY. 



SIR OLIVER LODGE, in the Trueman Wood 

 lecture to the Royal Society of Arts, referred to 

 last week, asked whether atomic energy may not 

 already be being unconsciously utilised. The recogni- 

 tion of radio-activity as a process of natural transmuta- 

 tion, in which a large and previously unknown store of 

 energy associated with the atomic structure is released 

 in the disintegration of the atom and its change into 

 totally different kinds of atoms, dates, of course, from 

 the early years of the century. The natural conclusion 

 is that, before this energy can be rendered available, 

 artificial transmutation must be possible, and that this 

 transmutation certainly does not occur in any other 

 case than in that of the radio-elements, and then only 

 spontaneously and in a manner not to be altered by 

 artificial means. 



Sir Oliver Lodge appears, however, to think that 

 internal atomic energy may be being already uncon- 

 sciously made use of, and cites two possible cases. 

 The first is vision. The retina is supposed to contain a 

 substance the atoms of which are capable of accumu- 

 lating a few million impulses of ather-waves of 

 luminous frequency. This causes the atom to eject 

 one or more electrons, and it is these electrons rather 

 than the original light-waves which stimulate the 

 nerve-endings. Even "accepting this as an interesting 

 and suggestive new photo-electric theory of visicn, 

 which accounts satisfactorily for the extreme sensitive- 

 ness of the eye, the energy involved is surely the 

 ener<*y of the exciting radiation rather than internal 

 atomic energy. Photo-electric effects in general are 

 not supposed to be different from or more- fundamental' 

 in character than other electro-chemical effects. 



In the other example it is the energy of the electrons 

 emitted bv an incandescent wire which is in question. 

 It is possible to welcome and recognise the very great 

 advance which the use of this phenomenon, by means of 

 the thermionic valve, has achieved in wireless telegraphy 

 and telephony, without accepting the view that any 

 new form of energy is utilised. The emission of elec- 

 trons is, indeed, described as analogous to the evapora- 

 tion of molecules from a surface, the velocities being 

 distributed in accordance with Maxwell's law for a 

 monatomic gas. It would seem sufficient to ascribe 

 the energy of the electrons to heat energy, at least 

 until it is proved that it is not so derived. The mere 

 latter-day interpretation of many of the changes 

 studied bv the chemist and electro-chemist in terms 

 of the electron does not alter their character, which is 

 well understood bv chemists not to be of the type 

 they would regard as transmutational. or tp_ involve 

 the' kind of energy disclosed by radio-activity, or. 

 indeed, any other kind than what has been familiar in 

 chemical, electro-chemical, and physical changes since 

 these subjects began to be studied. 



