428 



NA TURE 



[March 3, 1892 



marked, and the spectra of the third type may be divided into 

 four classes. In the fourth of these classes the hydrogen lines 

 are bright instead of dark. This spectrum seems to be charac- 

 teristic of the variable stars of long period when near their 

 maximum. As stated above, it has led to the detection of several 

 new variable stars, and has been confirmed in many of the 

 known variables. Slight peculiarities are noticed in the specira 

 of many stars, so that they cannot be arranged in an exact 

 sequence ; but these deviations are not sufficient to affect the 

 general law. The number of stars not included in the above 

 classification is very small. A few stars like 7 Cassiopeise, 

 3 Lyrce, and 5 Centauri resemble the stars of the Orion type, 

 but some of the lines are bright instead of dark. Stars of the 

 fourth type, whose spectra appear to be identical with that of 

 carbon, are not included in the above classification. Other stars, 

 whose spectra consist mainly of bright lines, like those of the 

 planetary nebulae, may be included with them in a fifth class. 

 It also appears that the position of the lines in both cases is 

 probably identical with that of corresponding lines in stars of 

 the Orion type." (Introduction, p. xvii.) 



It would be difficult to find fault with the masterly way in 

 which Prof Pickering and his assistants have done their work. 

 Our chief source of complaint, which no doubt arises more from 

 impatience than anything else, is the lack of detail with regard 

 to the specira themselves. For investigations to which such 

 a work as the Draper Catalogue should naturally lead, a mere 

 estimation of the type of spectrum serves for little more than a 

 determination of the relative numbers and distribution of the 

 spectra of the various types. For the present, however, this is 

 practically all that Prof. Pickering tells us. We are left quite 

 in the dark, for instance, as to what is actually seen in the 

 photographs of the spectra of stars of Secchi's fourth type, 

 although we are informed that the photographic spectra are as 

 characteristic as the visual. It would be interesting too, to know 

 the differences in the sub-divisions of Secchi's third type. 



All stars north of - 20° of the fourth magnitude and brighter 

 have been photographed on a large scale with the ii-inch re- 

 fractor, and a discussion of these will occupy a subsequent 

 volume of the "Annals." This will be awaited with interest 

 by all who are engaged in researches in astronomical physics. 



We are delighted to find that the work of the Plenn- Draper 

 Memorial is to be extended beyond the mere routine of photo- 

 ■graphing stellar spectra. "A broader field has been assigned 

 to the Henry Draper Memorial by Mrs. Draper than was at 

 first proposed. Instead of confining its work to the study of 

 the specira of the stars, their physical properties in general will 

 be investigated. The liberal support given to it should give yet 

 more striking results in the future than have hitherto been 

 attained." (introduction, p. xxiv.) 



Laboratory work has already been commenced, and to aid 

 the study of spectra in the electric arc, a lo-h.p. dynamo has 

 been generously presented by the Edison Electric < o. 



In the final chapter the Draper Catalogue is discussed with 

 reference to the visual observations of Vogel and Konkoly. A 

 similar comparison has already been given in Nature, vol. xliv. 

 p. 133, by Mr. Espin, and we need not further refer to it. We 

 regret to find, however, that a discussion of the photographic 

 spectra in relation to the new cla>sification suggested by Mr. 

 I.,ockyer has not been included. 



It will be a source of gratification to Mr. Lockyer to find that 

 his suggestion that stars of the Wolf-Rayet type are the first 

 results of nebulous condensations is fully confirmed by Prof. 

 Pickering's work. Their spectra greatly resemble those of the 

 planetary nebulas, the chief diffisrence being that the charac- 

 teristic nebula line near wave-length 500 is absent. This, Mr. 

 Lockyer explains, is due to increased temperature, and this 

 view is strengthened by the fact that the line was seen only during 

 the later stages of the visibility of Nova Cygni. Nebulae and 

 bright line stars form Group I. of his classification. 



So far, this is the chief point where the r)raper Catalogue 

 throws any additional light on Mr. Lockyer's views, and further 

 discussion must be reserved until more details of the spectra are 

 published. 



The " distribution of spectra" forms the subject of chapter 

 vii., and we gather that the stars down to magnitude 625 are 

 distributed as follows among the different classes of spectra : — 

 Class A ... 061 I Class K ... o-i8 



,, B ... 002 ,, M ... 0013 



,, F ... o*i2 "Peculiar" ... 0*007 



,, G ... 0-05 I 



NO, II 66, VOL. 45] 



" According to Secchi's classification, placing Classes A, B, 

 and F in the first type, G and K in the second, and M in the 

 third, we have of the first type 075, of the second 0*23, of the 

 third o-oi, fccuhar 001 " (p. 151). 



To study the distribution in sp-tce, the sky was divided into 

 48 zones, and the results are thus summarised on p. 152. "It 

 appears that the number of stars of the second and third type is 

 nearly the same in the Milky Way as in other parts of the sky. 

 Considering, therefore, only the stars whose spectra resemble 

 that of our sun, we should find them nearly equally distributed 

 in the sky. The stars of Class A, on the other hand, are twice 

 as numerous in Region M (through which the Milky Way 

 passes) as in Region N (an equal area away from the Milky 

 Way), and in the case of Class B this ratio exceeds four. The 

 Milky Way is therefore due to an aggregation of stars of the 

 first type, a class to which our sun seems to bear no resemblance 

 as regards its spectrum. Spectra of Class B seem to conform 

 still more closely to the region of the Milky Way, although 

 probably thry are not sufficiently numerous to materially affect 

 its light. The Milky Way must therefore be described as a 

 distinct cluster of stars to which, from its composition or age, 

 the sun does not seem to belong." 



The statement that the sun bears no resemblance to stars like 

 those which chiefly constitute the Milky vVay is not quite so 

 precise as it might be. The lines in the spectra, so far as we 

 know them, indicate the same substances in each, and the 

 tendency of evidence is to show that the sun is a type of what 

 the stars of the Milky Way will become. 



Nor the least interesting part of the researches connected with 

 the formati n of the Draper Catalogue is that dealing with the 

 determination of photographic magnitudes. Elaborate investi- 

 gations have been carried out by Prof. Pickering wiih his usual 

 skill and care, and we hope to refer to them in some detail on 

 another occasion. 



No satisfactory method of applying the slitless spectroscope to 

 the determinatiim of velocities in the line of sight, except in the 

 special case of a spectroscopic binary, has yet been devised, and 

 this branch of research must therefore be carried out in the usual 

 way. A. Fowler. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Oxford. — We regret to notice that the Savilian Professor of 

 Geometry (J. J. Sylvester, Hon. D.C. L.), has had to apply for 

 leave of absence and dispensation from the performance of 

 statutory duties on account of ill-healih, Mr. J. Griffiths, 

 Fellow and Tutor of Jesus College, will lecture on the " Recent 

 Geometry uf the Circle and Triangle " for the Professor. 



At a meeting of the Hebdomadal Council, Rev. W. Inge, 

 Provost of Worcester College, and Rev. W. W. Jackson, 

 Rector of Exeter College, were elected to be members of the 

 Delegacy for the Training of Teachers under the provisions of 

 the Statute approved by Convocation, November 24, 1891 ; and 

 in a Congregation holden February 23, Joseph Wells, Fellow of 

 Wadham College, and George K. Scott, Fellow of Mcrton 

 College, were likewise elected members of the same Delegacy. 



In a Convocation holden on March 1, Mr. Henry Balfour, 

 Trinity College, was appointed Curator of the Pitt- Rivers 

 Museum, to hold office until December 31, 1898, and during 

 that period to enjoy the same status in regard to the University 

 Museum as the Professors teaching in the Museum, and 

 to receive a stipend of ^200 a year from January i, 1892. 

 The Curators of the University Chest were authorized to 

 expend a sum not exceeding ;^I50 a year from January i, 1892, 

 for seven years, on assistance and current expenses in the Pitt- 

 Rivers Museum. 



Cambridge. — Mrs. Phillipps offers to the University a sum 

 of ;^20OO to found an "Arnold Gerstenberg Scholarship " in 

 memory of her brother. The Scholarship is to be held by men 

 or women who have passed the examination for the Natural 

 Sciences Tripos and intend to pursue the study of mental and 

 moral philosophy. 



A grant of ;^40 has been made to H. Kynaston, B.A. of 

 King's, from the Worts Fund, to enable him to investigate 

 the geology of the Eastern Alps in the ensuing summer. 



Prof Foster is appointed an Elector to the Downing Profes- 

 sorship of Medicine, to the Professorship of Zoology, and to 



