July 26, 1912] 



SCIENCE 



105 



to Sir John Hersehel at the Cape of 

 Good Hope, in 1833, mentions that her 

 brother, when examining the constellation 

 of the Scorpion (which lies at best low 

 down on our horizon), had exclaimed, 

 "after a long, awful silence, 'Hier ist 

 wahrhaftig ein Loch im Himmel. ' " And 

 her nephew, as he said, rummaged Scorpio 

 with the telescope and found many blank 

 spaces without the smallest star. 



It will explain some of the deductions 

 which Hersehel drew from his star-gauges, 

 and will at the same time furnish a good 

 example of his style, if I read a passage 

 from a paper of his written in 1789.^ He 

 points out that the sun is merely a star, 

 and, referring to the stars, he continues 

 thus: 



These suns, every one of which is probably of as 

 much consequence to a system of planets, satellites 

 and comets, as our own sun, are now to be con- 

 sidered in their turn, as the minute parts of a pro- 

 portionally greater whole. I need not repeat that 

 by my analysis it appears that the heavens consist 

 of regions where suns are gathered into separate 

 systems, and that the catalogues I have given com- 

 prehend a list of such systems; but may we not 

 hope that our knowledge will not stop short at the 

 bare enumeration of phenomena capable of giving 

 us so much instruction? Why shoiild we be less 

 inquisitive than the natural philosopher, who some- 

 times, even from an inconsiderable number of 

 specimens of a plant, or an animal, is enabled to 

 present us with the history of its rise, progress 

 and decay? Let us then compare together, and 

 class some of these numerous sidereal groups, that 

 we may trace the operations of natural causes so 

 far as we can perceive their agency. The most 

 simple form, in which we can view a sidereal sys- 

 tem, is that of being globular. This also, very 

 favorably to our design, is that which has pre- 

 sented itself most frequently, and of which I have 

 given the greatest collection. 



But, first of all, it will be necessary to explain 

 what is our idea of a cluster of stars, and by what 

 means we have obtained it. For an instance I 

 shall take the phenomenon which presents itself in 

 many clusters. It is that of a number of lucid 



» Phil. Trans., Vol. LXXIX., p. 212. 



spots, of equal luster, scattered over a circular 

 space, in such a manner as to appear gradually 

 more compressed towards the middle, and which 

 compression, in the clusters to which I allude, is 

 generally carried so far, as, by imperceptible de- 

 grees, to end in a luminous center of an irre- 

 solvable blaze of light. To solve this appearance 

 it may be conjectured that stars of any given very 

 unequal magnitudes may easily be so arranged, in 

 scattered, much extended, irregular rows, as to 

 produce the above described picture; or, that stars, 

 scattered about almost promiscuously within the 

 frustum of a given cone, may be assigned of such 

 properly diversified magnitudes as also to form 

 the same picture. But who, that is acquainted with 

 the doctrine of chances, can seriously maintain 

 such improbable conjectures? 



Later in the same paper he continues : 



Since then almost all the nebulae and clusters of 

 stars I have seen, the number of which is not less 

 than three and twenty hundred, are more con- 

 densed and brighter in the middle ; and since, from 

 every form, it is now equally apparent that the 

 central accumulation or brightness must be the 

 result of central powers, we may venture to afSrm 

 that this theory is no longer an unfounded hy- 

 pothesis, but is fully established on grounds which 

 can not be overturned. 



Let us endeavor to make some use of this impor- 

 tant view of the constructing cause, which can thus 

 model sidereal systems. Perhaps, by placing be- 

 fore us the very extensive and varied collection of 

 clusters and nebulse furnished by my catalogues, 

 we may be able to trace the progress of its opera- 

 tion in the great laboratory of the universe. 



If these clusters and nebulas were all of the same 

 shape, and had the same gradual condensation, we 

 should make but little progress in this enquiry; 

 but as we find so great a variety in their appear- 

 ances, we shall be much sooner at a loss how to 

 account for such various phenomena, than be in 

 want of materials upon which to exercise our 

 inquisitive endeavors. 



Let us, then, continue to turn our view to the 

 power which is molding the different assortments 

 of stars into spherical clusters. Any force, that 

 acts uninterruptedly, must produce effects propor- 

 tional to the time of its action. Now, as it has 

 been shown that the spherical figure of a cluster 

 of stars is owing to central powers, it follows that 

 those clusters which, ceteris pariius, are the most 



