6/6 



NATURE 



[January 20, 192 1 



tinent so well revealed in north-western Europe. The 

 main folding, however, in Bohemia and Moravia, 

 accompanied by great intrusions of granite and the 

 formation of large areas of gneiss, occurred in con- 

 nection with the "Variscan" movements — that is, in 

 Upper Devonian and Lower Carboniferous times — 

 thus heralding, and still at a long distance, the 

 Armorican movements of the west. This fact is 

 emphasised by Radim Kettner, writing from Pf'bram 

 (1917, p. 251). 



In the same year (p. 267) J. Woldi'ich exammed 

 the Cretaceous fauna of Neratovic, where concretions 

 containing 50 per cent, of calcium phosphate interest- 

 ingly occur. This discovery is compared with the 

 presence of phosphatic nodules in the Cretaceous of 

 France and England, and (p. 321) the fauna is 

 described in relation to its western representatives. 

 In the volume for 1915 (p. i) C. Zahdlka contributes 

 a far-reaching memoir on the Cretaceous system in 

 the Sudetic region and its equivalents in the western 

 lands of Central Europe. This includes many pleasant 

 references to the comradeship shown to the author by 

 French geologists, and the name of Valmy, where 

 the First Republic answered the proclamation of the 

 coalised kings, appears here happily (p. 109) in con- 

 nection with field-work on the zone of Inoceramus 

 lahiatus. There is much in this extensive paper to 

 interest English geologists, who must, by the way, not 

 overlook Richard J. Schubert's paper (1915, p. 277) 

 on otoliths of Barton Cliff in Hampshire, collected 

 bv H. Elliot Watson and sent to the author by Col. 

 C. D. Shepherd. Schubert's death at the head of 

 his company in the heroic ficrht at Gorlice on the 

 Russian front (obituarv by O. Ampferer, 1915, p. 261), 

 removed a very active and much-lovpd personality 

 from the ranks of the Reichsanstalt. 



British and Indian geologists may also note Rudolf 

 Zubef's contributions to the geologv of the Punjab 

 (1914, p. 327), resulting from explorations organised 

 bv an English oil company in 1013. There are two 

 highlv sugg-estive diagrams showing the interlocking 

 of different types of Eocene strata, including the salt- 



clay series, and their folding in the great Himalayan 

 movements to form the present Salt Range. 



Broad questions of petrography have not escaped 

 the attention of the Reichsanstalt, such as Bruno 

 Sander's "Beitrage aus den 2^ntralalpen zur Deutung 

 der Gesteinsgefijge " (1914, p. 567), in which the 

 stratified and folded structures in many crystalline 

 rocks are recognised as of earlier date than the crystal- 

 lisation of their present mineral constituents; or the 

 extensive study of peridotites and their allies involved 

 in F. Kretchmer's memoir on "Der metamorphe 

 Dioritgabbrogang im Spieglitzer Gebirge" (1917, p. i). 

 Palaeontology is represented by. a number of shor 

 papers, including one by J. V. Zelizko (1918, p. 113) 

 on a small species of lion from the Pleistocene of 

 Wolin, in southern Bohemia. One large folio memoir, 

 on Oxynoticeras, by J. von Pia, was issued in 1914; 

 it includes the usual considerations in regard to what 

 constitutes a genus or a species, to which we are 

 accustomed when ammonites are brought into the 

 arena. In critical biography E. Tietze's " Einige 

 Seiten iiber Eduard Suess " (1916, p. 333), a paper of 

 more than 200 pages, is a very memorable review of 

 the recent history of geology. Even the papers on 

 economic subjects reflect the calm detachment of the 

 institute, encouraged to carry on its work with a 

 cosmopolitan outlook, during a catastrophe that has 

 broken the bonds of man to man by more than in- 

 exorable death. Even F. von Kerner's studv (1016, 

 p. 141;) of the water-supply in the Middle Dalmatian 

 karst-res:ion, with its valuable series of sections, will 

 be to the advantage of the Slavonic peoples rather 

 than to those who blasted their trenches on the Carso 

 in the hope of retaining a sovereigntv at Trieste. And 

 so, indeed, it should be alwavs. The Austro-Hun- 

 garian Festland has become broken into horsts and 

 Graben ; but will not time smooth the fault-scarps 

 that now loom up as separating walls? The best 

 guarantee of scientific co-operation is to be seen in 

 the names of those who have, during years of bitter- 

 ness and division, contributed in serene hopefulness 

 to the sum of human knowledge. 



Measurements of the Angular Diameters of Stars. 



AFTER the successful measurement of Capella as 

 a double star by Prof. A. Michelson's interfero- 

 meter method applied to the loo-in. reflector at 

 Mount Wilson, it was known that he intended to 

 attempt the more difficult feat of measuring stellar 

 diameters. The most hopeful stars to choose for the 

 purpose are the giant red stars. Prof. Eddington 

 made some estimates of their angular diameters in 

 his inaugural address to Section A of the British 

 Association last August (Nature, September 2, 1920, 

 p. 14). Taking the temperature and surface bright- 

 ness derived from the distribution of energy in the 

 spectrum, the angular diameter (which is independent 

 of the assumed distance) is deducible from the 

 apparent magnitude. The highest estimate for 

 any star was that for Betelgeux, the value being 

 0-051". 



The daily Press of December 31 announced that 

 Prof. Michelson read a paper before the American 

 Physical Society in which he stated that he had 

 determined that the diameter of Betelgeux was 

 260,000,000 miles, or three hundred times that of the 

 sun. As the assumed distance of the star was given 

 as 150 light-years, we may infer that the measured 

 anfrular diameter was 0061'' — a close agreement with 

 Prof. Eddington 's estimate.' Once the angular dia- 



1 A later communication gives 0*046" as the measured diameter. 



NO. 2673, VOL. 106] 



meter of a single Ma star is determined, those of 

 all the stars of the same spectral type can be deduced 

 from their apparent magnitudes. The huge bulk of 

 Betelgeux is a striking illustration of Prof. H. N. 

 Russell's theory of giant and dwarf stars. Its density 

 is presumably very low, otherwise an improbably high 

 value of the mass would result. 



Some further details of the result obtained at Mount 

 Wilson were communicated in a letter from Prof. 

 G. E. Hale which was read at the meeting of the 

 Royal .Astronomical Society on January 14. The 

 apparatus consists of two periscopes fixed to a frame 

 at the object-end of the tube of the loo-in. Hooker 

 reflector. The outer mirrors are some 20 ft. apart, 

 but the distance is capable of being varied. The inner 

 mirrors are about 4 ft. apart ; this is merely a matter 

 of convenience, the beams being brought down the tube 

 on opposite sides of the Cassegrain mirror. .An addi- 

 tional plane mirror is used for reflecting the light up 

 the polar axis. The measurement of a star's diameter 

 is effected by varying the distance between the outer 

 mirrors and finding the points at which the interfer- 

 ence fringes disappear. The actual observation is 

 very tedious and difficult ; it was stated that half an 

 hour was required each time the mirror was moved 

 before the visibility of the fringes could be tested. 

 Moreover, in measuring a star disc, observations are 



