December io, 1914] 



NATURE 



401 



law," and we now have Planck's atom of energy-, 

 which seems destined to play an important part in all 

 future advance, while matter itself — the indestructible 

 matter of Lavoisier — recedes into the background to 

 consort with such shades as velocity and acceleration. 

 In a "Sketch of a Generalised Theory of Relativity 

 and a Theory of Gravitation " (B. G. Teubner, 19 13 ; 

 pp. 38) Prof. Einstein, in collaboration with Dr. Gross- 

 mann, gives a preliminary account of their attempts 

 to base the whole structure of theoretical physics upon 

 .the assumption of an exact proportionality between 

 hea\y and inert mass, and consequently upon what 

 Einstein calls "the h^J)othesis of equivalence." The 

 meaning of the latter is : an obser\-er enclosed in a 

 box cannot decide whether the box rests in a statical 

 gravitational field or is endowed with accelerated 

 motion in a space free of gravitation. This leads to 

 the requirement of universal invariance of a quadratic 

 form in dx, dy, dz, dt with variable coefficients (which 

 determine the gravitational field), instead of the ven,' 

 simple Lorentz-invariant of the "ordinary theory of 

 relativity." Electromagnetic phenomena become 

 entangled with gravitation ; constancy of light-velocity 

 is given up, of course ; the Maxwell-Lorentz equations 

 for a vacuum assume a generalised and more com- 

 plicated form. Similar investigations are to be found 

 in Kottler's paper of 1912 {Wien. Berichte, vol. cxxi.). 

 There are many other striking consequences of the 

 new theorj% which obviously cannot be entered upon 

 here. The " physical part " of the paper is written by 

 Einstein, the "mathematical" part by Grossmann. 

 Their theory, apart from undesirable complications, 

 is far from being complete, since, as the authors 

 themselves confess, they have not been able to find 

 the general group of substitutions for their gravita- 

 tional equations. We may remark here that, for- 

 tunately, there is thus far no urgent need of such 

 generalisations, especially as Nordstrom 's theory of 

 gravitation based upon the " old " principle of relativity 

 satisfies all reasonable requirements. 



The Journal of the Institution of Electrical 

 Engineers for December i contains an account of 

 some interesting experiments made at the National 

 Physical Laboratory by Messrs. S. W. Melsom and 

 H. C. Booth on the temperature rise in twin flexible 

 wires such as are employed in ordinary electric light 

 installations for pendant lamps with shades. It was 

 found that, with lamps consuming 55 watts and up- 

 wards the temperature rise at the cord grip was in 

 many cases 24° C. or more, that is to say, twice that 

 allowed by the wiring rules of the institution, and 

 high enough to destroy gradually the rubber insula- 

 tion on the wire and to weaken the silk covering. 

 This was due to heat from the lamp, and was irre- 

 spective of any heating of the wire itself due to the 

 current passing. Similar observations were made in 

 the case of flexible wires leading to electiic irons, hot 

 plates, etc. The temperature observations were in all 

 cases made by means of minute thermo-junctions 

 placed at the points tested. The results of the inves- 

 tigation emphasise the desirability of periodically re- 

 newing these flexible wires without waiting for them 

 to show outward signs of deterioration. 



NO. 2354, VOL. 94] 



OUR ASTRONOMICAL COLUMN. 



Distribution of Elements in the Solar Atmo- 

 sphere. — No. 88 of the Contributions from the Mount 

 Wilson Observatory contains the results of an investi- 

 gation on the distribution of the elements in the solar 

 atmosphere as given by flash spectra, contributed by 

 Mr. Charles E. St. John. The spectrum used in this 

 research was that which was obtained by Prof. 

 Mitchell during the 1905 eclipse, and the results of the 

 reduction of this spectrum, which have already been 

 published, are here employed as the basis of the statis- 

 tical discussion here described. The general scheme 

 in this research has been to form numerous groups of 

 lines on a simple plan, each element being considered 

 by itself, and the lines of like solar intensity assigned 

 to it forming the ultimate group. The results of the 

 'investigation are considered in relation to the author's 

 previous conclusions regarding the distribution of the 

 elements as deduced from the radial motion in sun- 

 spots, and he draws a series of general conclusions 

 founded on the salient facts shown by flash spectra 

 and displacements in the penumbras of sun-spots 

 based upon mean values. These are too numerous to 

 be given here, but the author points out that " these 

 facts are all harmonised by the consideration that the 

 vapours of the elements ascend in detectable amounts 

 to different heights, that the lines of any one element 

 originate at depths increasing with decrease of solar 

 intensit}-, that the enhanced lines are higher than un- 

 enhanced lines of equal solar intensity, and that we 

 see into the sun to greater depth at the red end of 

 the spectrum than at the violet." A general summary 

 states that "the resulting distribution shows that H3 

 and K3 lines of calcium are the lines of highest level, 

 followed by the Ha line of hydrogen, and that, in the 

 main, the hea\y and rare elements occur in detectable 

 amounts only in the lower portions of the solar atmo- 

 sphere." 



Photographs of H.\lley's Comet and Comets of 

 THE Year 1911. — In the Annalen der k.k. Universitdts- 

 Sternwarte in Wien (vol. xxiii.. No. i) Dr. Joseph 

 Rheden publishes a valuable memoir containing de- 

 tails about the photographs which he secured of 

 Halley's comet in 1910 and other comets in 1911. 

 Several instruments (on one equatorial mounting) 

 were employed, such as an objective of 325 mm. 

 aperture and 34 m. focal length, a Voigtlander 

 portrait anastigmat of //4-5, with focal lengths 

 of 450 or 225 mm., and, lastly, a Zeiss-Planar //3-6 of 

 no mm. focal length, and another of //3-5 of 100 mm. 

 focal length. The memoir contains a brief descrip- 

 tion of the details of each of the photographs taken 

 and numerous excellently reproduced plates illustrate 

 the general forms of the various comets photographed. 

 Besides Halley's comet, those of Kiess (fc). Brooks 

 (c), Qu^nisset (/) and Beljawsky {g), are discussed. 

 It is interesting to note that attempts were made 

 with two different instruments to record the transit 

 of Halley's comet across the solar disc on May 19, 

 but the weather was not very favourable, and the 

 results not of a satisfactory nature. 



Strange Objects Transiting the Sun's Disc. — In 

 scanning the solar surface obser\-ers have often re- 

 marked that they have seen bright objects passing 

 across the sun's surface, and have concluded that 

 they were meteors in the absence of any other plausible 

 explanation. Attention may be directed to two in- 

 teresting letters dealing with this subject which are 

 communicated to the Observatory for November by 

 Prof. Barnard and Mr. Denning. They put before 

 the reader a large number of instances when such 

 objects were observed, and decide conclusively that 

 these davtime showers are not meteors. Mr. Dennine 



