S6 



NA TURE 



[May 1 6, 1901 



which has been made was therefore very desirable, and 

 we feel sure that the addition of a representative of 

 science to the committee will meet with general approval. 



As the methods of selecting candidates for the Army 

 have been altered repeatedly during the last twenty 

 years, and as the present regulations, which we owe 

 largely to the exertions of Sir Henry Roscoe, came 

 into action no later than November 1898, it is clear 

 that only an exceedingly small proportion of our 

 present officers have been selected under those regula- 

 tions and that only a few of these can as yet have reached 

 positions higher than that of a lieutenant. It is certain, 

 therefore, that any defects that may have been detected 

 during the trials of the last two years must, so far as 

 they are due to systems of selection at all, be the out- 

 come, not of the present system, but of those narrower 

 schemes which preceded it, and which, as we pointed 

 out again and again before they were altered, tended to ex- 

 clude certain classes of candidates from a profession which 

 they were well fitted to adorn. This defect was remedied 

 by the regulations now in force, and we trust that what- 

 ever changes may be found necessary there will be no 

 reverting at this critical moment to the narrower policies 

 of the earlier scheme. 



There is said to be a strong and, we would venture to 

 add, a highly reasonable feeling on the part of leading 

 military authorities that what the Army wants is a 

 plentiful supply of able candidates. If this be true, as 

 we hope it is, we trust that the committee may find 

 themselves able to make recommendations which will 

 enable clever candidates who may not happen to be 

 endowed with private incomes, or to be cadets of 

 well-to-do families, to enter the Army more freely 

 in the future than has been possible in the past. 

 And, secondly, that they will take care that any new 

 scheme of examination they may propose shall have no 

 tendency to restrict the field of selection, but offer rea- 

 sonably equal chances, as the present scheme does, to 

 candidates of all suitable types and aptitudes. It would 

 be a national misfortune if any present necessity of the 

 .Army should be made the basis of changes which would 

 tend to reproduce the conditions of ten or a dozen years 

 ago. 



STUDIES ON THE STRUCTURE OF THE 



UN/VERSE.^ 

 A VERY interesting publication has recently been 

 -'*■ issued by Mr. Stratonoff, of the Russian Observa- 

 tory at Tachkent, on the structure of the universe, a 

 problem which has a fascination of its own for most 

 readers quite apart from any real progress which may 

 be made towards its solution. 



The question is so vast that the researches of our 

 greatest astronomers have done little more than lead us 

 to the top of Pisgar and show us from afar the pro- 

 mised land, but every newly ascertained fact, or even 

 confirmation of old ones, is a valuable contribution to- 

 wards the general stock of knowledge which is being 

 gradually accumulated, out of which, perhaps, the genius 

 of some future Newton may evolve some general law. 



Before any real advance can be made in the study of 

 the structure of the universe, it is necessary to commence, 

 and perhaps finish, with the Milky Way, that great band 

 of faint stars which has puzzled mankind from the earliest 

 times and which has been explained more according to 

 the imagination of the observers than with any regard to 

 the facts. Indeed, before the age of modern scientific 

 instruments there were no facts to explain anything, and 

 even now, with all our present resources, fresh facts are 

 only being very slowly brought out ; we still depend very 



i'" Publications de rObservatoire Astronomique et Physique de Tachkent. 

 Etudes sur la Structure de I'Univers," par W. Stratonoff, Astrophysician de 



NO. 1646, VOL. 64] 



largely on eye observations, only the eye we now use is 

 the photographic camera. 



We know in a general way that the galaxy is composed 

 of very faint stars, presumably at an immense distance 

 from our system, and that the stars have a tendency to 

 thin out as we leave this region and approach the galactic 

 poles. The great researches of Herschel, W. Struve, 

 Argelander and Seeliger have thrown much light on the 

 distribution of the larger stars as shown in the various 

 catalogues ; there, however, still remained the telescopic 

 stars to deal with, and it is this part of the question that 

 Mr. Stratonoff has taken in hand. 



Mr. Stratonoff has devoted himself to the making of a 

 series of charts showing the distribution of the stars in 

 the northern hemisphere and down to 20° south, and for 

 this purpose he has divided the part of the sky dealt 

 with into iSoo separate areas, and tables are given show- 

 ing the density of the stars in each. These particulars 

 are represented in the maps by a colour scale by which 

 the regions containing the largest number of stars may be 

 seen at a glance. 



The first eight maps show the distribution of stars to 

 each half magnitude from the 6th to g'j ; and the well- 

 known tendency of the stars below the 6th magnitude to 

 leave the poles and crowd more and more towards the 

 galactic equator is well shown in the case of each mag- 

 nitude. 



The Milky Way itself Mr. Stratonoff considers to be an 

 agglomeration of immense condensations, or stellar 

 clouds, which are scattered round the region of the 

 galactic equator. These clouds, or masses of stars, some- 

 times leave spaces between them and sometimes they 

 overlap, and in this way he accounts for the great rifts, 

 like the Coal .Sack, which allow us to see through this 

 great circle of light. 



Mr. Stratonoff also finds evidence of other condensa- 

 tions of stars in these maps ; the nearest is one of which 

 our sun is a member, chiefly composed of stars of the 

 higher magnitudes, which thin out rapidly as the Milky 

 Way is approached. 



A second condensation is also found at a distance 

 represented by the stars of magnitudes from 6'5 to 8' 5, 

 and a third, still further off, at about the distance occupied 

 by stars of magnitudes from 7 '6 to 8. 



Mr. .Stratonofi" has also pushed his inquiries into the 

 distribution of the stars according to their spectral type. 



For the purposes of this inquiry the Draper Catalogue 

 has provided the materials. In this catalogue the stars 

 are divided into sixteen classes, known by letters from A 

 to Q. In order, however, to facilitate mapping, Mr. 

 Stratonoff has put all these classes into two : — Class I. 

 embraces the divisions A, B, C and D, and Class II. 

 takes in the rest. These two classes are too large to 

 make these two maps of the distribution of the spectral 

 types of much service, but they may be taken to give 

 some rough idea of the position in the heavens of the 

 stars of Secchi's types I. and II. From a glance at these 

 maps it is seen that the stars of type I., which includes 

 the Sirian and Orion stars, are situated principally near 

 the Milky Way, while those of type II., which includes 

 our sun, are principally condensed in a region coinciding 

 roughly with the terrestrial pole, and only show a slight 

 increase, as compared with other stars, as the galaxy 

 is approached. 



This mapping out of stars in their spectral classes is of 

 the highest interest in the study of the structure of the 

 universe, but we doubt whether the study of these types 

 is sufficiently advanced to get any real information which 

 can assist the student in this respect, and we must be 

 content to wait until a far larger number of stars has 

 been accurately observed before such maps can have 

 anything more than a passing value. Mr. Stratonoff, 

 however, has skilfully used the material he had, and we 

 hope that he will take up this part of his subject later on. 



