January 6, 191 6] 



NATURE 



521 



and a third is erected and riveted complete upon its 

 staging. In lowering the caisson, excavation within 

 the working-chamber proceeded until a pcint was ap- 

 proached about 5 ft. from foundation level ; at this 

 point the clay at each end of the chamber was not 

 removed, but allowed to come in contact with the 



M-ending roof of the chamber for a length of about 

 ft. from each end. The weight of the caisson, 

 Logether with the concrete and masonry, approximated 

 to 5000 tons, but there was full control of the move- 

 ments, and the downward travel was stopped easily 

 at the given level. 



TfiE Athenaeum will in future continue its issue 

 only as a monthly, and not weekly as heretofore. The 

 new number will be published on January 15, at the 

 price of a shilling. 



The Cambridge University Press announces the 

 forthcoming publication of vol. ii. of Dr. W. Ridge- 

 way's "The Early Age of Greece," and a new edition 

 of vol. i. of the work. The following "Cambridge 

 Tracts in Mathematics and Mathematical Physics " are 

 in preparation :—" The Definite Integral, its Meaning 

 and Fundamental Properties," by Dr. E. W. Hobson ; 

 ".•\n Introduction to the Theory of Attractions," by 

 Dr. T. J. I'A. Bromwich; "Pascal's Hexagon," by 

 H. W. Richmond; " Lemniscate Functions," by Dr. 

 G. B. Mathews ; " Chapters on Algebraical Geometry," 

 by Prof. H. F. Baker; and "The Integrals of Alge- 

 braic Functions," by Prof. H. F. Baker. 



OUR ASTRONOMICAL COLUMN. 



Comet 19156 (Taylor).— Several communications to 

 the Paris Academy of Sciences {Comptes rendtis, De- 

 cember 20) concern Taylor's comet. At the Lyons Ob- 

 servatory M. J. Guillaume obtained a brief observation 

 of the comet on December 6. \ feeble nucleus was seen 

 surrounded by a nebulosity about i' in diameter. Its 

 magnitude was 9-5 and the colour was bluish. Posi- 

 tions were measured on December 11 and 13, the 

 comet fading to 10-5 mag. M. Paul Briick has cal- 

 culated the following orbit from observations made 

 at Algiers (December 6), Lyons (December 11), and 

 by himself at Besan^on on December 14 : — 



Perihelion passage, 1916, February 26986. 



a. = 14- 13' 46"] 



^ = 107" 16' 10" [1915-0 



: = 22° 44' 23" J 



lopr g =0-22625 



This parabolic orbit represents the middle place with 

 rm error of —9" in longitude and —32" in latitude, and 



second calculation is to be made. With the first 



hemeris sent out from Copenhagen Prof. E. Strom- 

 ' n stated that the orbit was apparently periodic in 

 ort period. In Circular No. 497 (Astronomische 

 achrichten) Prof. H. Kobold directs attention to the 

 iiiilarity between Messrs. Braae and Fischer-Peter- 

 n's second orbit (Nature, December 23, 1915) 

 nd Lamp's elements for Brorsen's comet 01=14° 55-^'. 



= 101* 276', i = 2q° 23-8' (1890). 



An observation made at the Hill Observatory' on 

 [anuary i indicates an increasing lag between the 

 >met's actual position and that calculated from the 

 'lOve orbit, then amounting to about 30' of arc in 

 «th R..'\. and declination. The comet, easily seen in 



three-inch finder, had evidently increased in bright- 



ss by about 2h magnitudes since December 16. 



The Spectra of Woi.f-Rayet Stars. — A most signifi- 

 int clue to the relationships of these extremely in- 



NO. 2410, VOL. 96] 



teresting stellar bodies was afforded by an extra- 

 ordinaj-y piece of spectroscopic research carried out 

 at Mount Wilson upon the faint vestiges of several 

 novas. It was then practically established that in 

 their latest phases these bodies assume the well-known 

 Wolf-Rayet features. Hartmann's observations of 

 Nova Persei were confirmed and generalised. The sugges- 

 tion was made that the Wolf-Rayet stars were possibly 

 remnants of novae. Extremely important evidence 

 bearing on this point has now been brought forward 

 by Dr. Max Wolf (Astronomische Nachrichten, 4824). 

 He finds that in the case of several of these stars the 

 spectra are variable in the oscillatory mode hitherto 

 regarded as peculiar to the later stages of novae. The 

 variations are described as alterations in the hydrogen 

 bands, especially H8, whilst the absorption lines are 

 said to appear at titnes sharp, at others masked and 

 weakened. As Dr. Max Wolf refers to the limitations 

 of his instrumental equipment, developments must be 

 looked for elsewhere. A photometric study of the 

 same stars would most obviously be of great value. 



Photo-electric Photometry. — Messrs. P. Guthnick 

 and R. Prager announce {Astronomische Nachrichten, 

 4823) that the conjectured variability of a Cygni has 

 been confirmed by numerous photo-electric measures. 

 Minima were found, 1914, September 28 ±iod, and 

 1915, July 5, ± lod, the interval being a multiple of 

 the period. Amplitude 0-07 mag., probably in the 

 mode of 8 Cephei. Short period oscillations are indi- 

 cated. The variability of a Lyrae and y Lyrae has also 

 been evidenced. The light changes in both cases are 

 described as very rapid and strictly periodic for the 

 latter, a Lyrae, however, would seem to vary in a 

 novel manner, with an average amplitude of 004 mag., 

 7 Lyrae 003 mag. 



Some Possibly Connected Solar and Planetary 

 Phenomena. — An attempt has lately been made by Herr 

 T. Kohl to trace a connection between some planetary 

 phenomena and solar activity (Astronomische Nach- 

 richten, 4821). Thus he finds that Jupiter's northern 

 cloud belts appear to be especially weak at times of 

 spot maxima, and become broader and more con- 

 spicuous during minima. The recorded appearances 

 of the secondary light on the dark side of Venus are 

 too scanty for comparison, but the later observations 

 suggest coincidence in time with auroral displays on 

 earth. 



Determination of Radial Velocities by Objective 

 Prisms. — Nearly two years ago M. Hamy suggested 

 an ingenious method of adapting the prismatic camera 

 to line of sight work (Nature, vol. xcii., p. 616, Janu- 

 ary 29, 1914). Whilst the determination of radial velo- 

 cities of the fainter stars is actually largely in way of 

 being realised by increased telescopic power and suitable 

 spectrograph design rather than by the employment 

 of novel methods of attack, M. Hamy has not been 

 deterred from investigating further the theory of his 

 method. He now states (Comptes rendtis, No. 22, 

 1915) that the use of a train of prisms would only necessi- 

 tate a modification of the reduction formulae, and then 

 develops the requisite changes for the case of an in- 

 strument mounting two prisms. 



Radial Velocity of R Coron.^j Borealis. — Dr. H. 

 Ludendorff, in a note in the Astronomische Nachrich- 

 ten (No. 4823), publishes the results of some spectro- 

 scopic observations of R Coronae. Six spectrograms 

 were secured during June, 1913, and June, 1915, whilst 

 the variable was at normal brightness, as was the 

 case during earlier observations in 1902-1906. The 

 spectrum resembles that of a Persei, and no signs of 

 alteration could be detected. The mean radial velocity 

 for the six plates is 4-248 km. (range = 5 km.). The 

 earlier measures gave +24-7 (range = 6-4). The small 

 range, under the conditions, leaves undecided the 

 question of variability. 



