August, 1904.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



V 



until icx>i, and the cases of 53 stars are discussed. Tlicse 55 

 stars are divided into three classes accordins; to their types of 

 variation. There .are ei,t;ht sliort '• period stars of ll\c 

 t; .\i]ail;e .and ,.i Lyra* types: seven of types wliich m.iy he 

 called intermediate with periods of from 4(1 to 163 days ; .md 

 38 stars which are distinctly of the louf^-period type. In the 

 first class, where the stars h.ave .a short-period variability, there 

 does not seem to be any sussestiou of a relation between 

 colour .and length of period. In the second class, or '• inter- 

 mediate " stars, there is evident a marked progression in the 

 lengths of their periods, corresponding to that in their 

 observed colours. In the third class, consisting of 5S long 

 period stars, the correspondence between depth of colour and 

 length of period is so marked as to point strongly to some 

 real connection between the two. confirming Chandler's dic- 

 tum that •' The redder the tint, the longer the period." The 

 variation .also seems to become increasingly irregular. 



* * * 



The Spectroscopic Binary, ,3 Aurigae. 



Not quite a ye.ar ago. Mr. (',. A. Tikhot'f. from a discussion 

 of spectrograms of .-( .Auriga' taken at the Fulkowa ( )bser\a- 

 tory, concluded that the star is not merely double but (pi.-ul- 

 n;ple, being composed of two groups of bodies, each of whicli 

 consists of a star with strong lines and a second star willi 

 weak lines. The revolution of the two groups takes place in 

 slightly less than four days, but of the stars in each group in 

 one-fifth of this time. This inference was based on the com- 

 plex appearance occasionally presented by the H^line; and 

 caused Professor Vogel to set on foot a new seri(;s of observa- 

 tions of the star. These have not led him to support Mr. 

 TikhofTs views. By a very slight alteration of the adopted 

 period he was able to bring the 85 observations at his disposal 

 ver>' satisfactorily on a single curve ; and he concludes that 

 there is no sufficient reason to accept the quadruple structure 

 of the system. With a circular orbit and a period of ,5'<)59<) 

 days, and a rehative velocity of 222km., the mass of the system 



comes out .as 4-5 sin ^ / that of the sun, and the distance of the 

 two bodies apart as 11 sin i = 12.000.000 km. The radial 

 velocity of the system is found by Vogel to be — 2t + i km. 

 agreeing well with those found by Deslandres and Tiklioff. 



* » * 



The Visibility of Lines a-nd Wires. 



Mr. Lowell is following up liis earlier experiments as to 

 the extreme limits of visibility of lines and wires, and in 

 Bulletin 10 of the Flagstaff Observatory, he gives the results 

 obtained by two of his assistants. These found it possible to 

 glimpse or suspect a line or wire when its angular width was 

 only o"'8 of arc. No marked difference was found between 

 the limit for a blue line ruled on white paper, and that for a 

 wire seen against the sky. 



* ■)(■ * 



Radial Velocities of the Pleiades. 



The Pleiades in general do not give spectra favourable for 

 determinations of radial velocities; they lack the metallic lines 

 seen in Sirian and solar stars, and the lines of helium are 

 usually weak and diffuse. Mr. Walter S. .Adams has been able 

 to deal with six stars of the group with some success; the 

 speeds deduced in kilometres per second being as follows : — 

 Merope + 6, Atlas + 13, Electra + 14, .Alcyone + 15, 

 Taygeta + 3, whilst Maia was found to v.ary in velocity. 

 Merope was ob.served with most difficulty, Maia with least ; 

 the first four stars showing spectra like those of nebulous 

 stars, whilst Taygeta and M.ii.i should possibly be regarded 

 as not physically connected with the nebulosity. 



An Expedition for Solar Research. 



Professor G. E. Hale is conducting an expedition to Mount 

 Wilson (58S6 feet), near Pas.adena, California, for the purpose 

 of making special investigations of the Sun. The chief instru- 

 ment will be the Snow horizont.il telescope recently constructed 

 at the Verkes Observatory. This consi.sts of a 30-inch C( clost.it, 

 with a 24-inch subsidiary mirror by which the light can be 

 deflected on one of two concave mirrors also of 24 inches 

 diameter. One of these has a focal length of 60 feet, the other 

 of 145 feet. The latter giving a i6-inch solar image will be 

 used in conjunction with a spectroheliograph of 7 inches aper- 



ture .and 30 feet focal length. Throe foc.il slits will be used 

 together, so that three different parts of the sjiectrum mav l»' 

 photographed simultaneously. Thedo-foot mirror is to be also 

 used in connection with .i spectroheliograph, but a special 

 attempt will be maile to photograiih with it sonu' of the 

 brighter stars, using a stellar spectrogr.iph provided with a 

 large concave grating .and mounted in .1 constaul tempcr.iture 

 Laboratory. 



* * X- 



Eclipse Problems. 



In the Pof'uUif Science Monthly for Jime, 1004, Professor W. 

 W. Campbell discusses the more important points of eclipse 

 problems. He first considers the (piestion of intramercm iai 

 planets. The experience of icjoi w.is almost but not (|uite 

 conclusive .against their existence ; if simil.ar successful pholo 

 graphs were taken in L.ibr.idor, Spain, Tunis, and Egypt in 

 1905 the (juestion would be settled one way or other. The re- 

 versing layer comes next. Additional work with more power- 

 ful instruments in perfect adjustment is reepiired ; and 

 esp<'cially photographs taken on continuously moving pl.iles 

 are needed, since exposures of two or four seconds iutegr;ite 

 the ch.anges which are going on. The chief problem is the 

 corona, since we do not yet know wliellier the m.aterial of the 

 stre.imers is moving outward, inw.u'd, or in both directions, or 

 in neither. It is essenfi.al that idcuticd instruments of long 

 focus be employed in at least three widely separated stations to 

 photograph the corona with .1 connnou scheme of ex|)osures. 

 Professor Campbell regards this (|uestion of coron.il movement 

 as the most import.mt of the coming eclipse. ( )ther problems 

 are the sources of light and heat for th(; outer corona, calling 

 for thcrmogr.iphic and polarigraphic observatiiuis ; the bright- 

 line spectrum of the inner corona in 1(105, ^f sun-spot maxi- 

 mum, comparing the thickness and uniformity of this siralum 

 with the results obtained ,it the recent eclipses at minimum ; 

 the .accurate determination of the wave length of the truly 

 coronal lines so that a serious effort may be made to represent 

 them by a simple couunon law, ;is with hydrogen and helium. 

 Professor C.-inipbell concludes with insisting on the need lor 

 insuring against person.al failures by at once making the fullest 

 possible preparation. I'''ailurcs in the p.ast have been Largely 

 due either to attempting too large a programme for the time 

 of totality, or more usually to want of adequate experience of 

 the instruments or methods employed. 



ORNITHOLOGICAL. 



Bv W. P. PvcRAFT, A.L.S., F.Z.S., M.B.O.LL, &.c. 



Killdeer Plover in Aberdeenshire. 



Ki;ai)i;rs of this column will prob.ibly be interested in the 

 fact that I have just discovered an undoubtedly Piritish-killed 

 example of the Killdeer Plover [.litiialitis. vmifcra) in the Uni- 

 versity Museum of Aberdeen, though for tiiirty-seveu ye.irs it 

 has passed for the common ringed Plover (./■,'. hi(ilicuta). The 

 label on this specimen runs as follows : " Cluiriulrins hinticuta, 

 Ringed Dotterel, sliot .it Peterhead by Andrew Mnrr.iy, 

 jun.. Esq., 1867." 



From this Libel, which is yellow with .age, there can be no 

 doubt but that this bird was presented by the donor simply 

 as a common ringed dotterel. To .allay all doubt, Professor 

 J. Arthur Thomson, in whose care this bird now rests, has 

 kindly interviewed Mr. Murray for me, and he distinctly 

 recollects the circumstance in connection with this incident. 



The Killdeer Plover is .admitted into the British list by Mr. 

 Howard Saunders on a single example shot at Tresco. Scilly 

 I.slands, and described in the Zooloi;iHt for 1SS5, p. r 12. 



* * * 



Yellow-legged Herring Gull at Dover. 



At the Last meeting of the Ornithologists' Club, held June 15, 

 the I Ion. N. Charles Rothschild recorded that he had observed 

 in DoverH.arbour, on April 18 Last, a bird which he considered to 

 have been an example of the \'el low -legged Herring Cidl {l.iinis 

 cachinnaus). The bird in question was flying in company with 



