September 15, 1911] 



SCIENCE 



325 



But, having now accumulated a large mass 

 of observation, he is proceeding to let them 

 tell their own tale, and a wonderful story it 

 is. We have, unfortunately, not time to 

 listen to more than a fraction of it at the 

 moment; but that fraction is well worthy 

 of our attention. When the stars are 

 grouped in classes according to their spec- 

 tral type, their average velocities differ; 

 and if the spectral types are arranged in 

 that particular order which for quite inde- 

 pendent reasons we believe to be that of 

 development of the stars, there is a steady 

 increase in the velocities. To put the mat- 

 ter in a nutshell, the older a star is the 

 quicker it moves. There are, no doubt, sev- 

 eral assumptions made in reducing the 

 matter to this simple statement, but I ven- 

 ture to think that they do not affect the 

 point I now wish to make, which is as fol- 

 lows. There is no doubt whatever that the 

 catalogue of facts accumulated by Mr. 

 Campbell, when arranged in an obvious 

 order, has led to a most important scientific 

 generalization — a direct negative at this 

 date of Sir George Darwin's opening sen- 

 tence, however true it may have been when 

 he wrote it. If we read on, his next sen- 

 tence doubtless entitles him to say that it 

 was the marshaling of the facts which led 

 to the conclusion. It is not altogether clear 

 to me in what way this marshaling differs 

 from the permitted "arrangement" of the 

 catalogue; but the third sentence seems to 

 imply that the distinction lies in the exist- 

 ence of a theory. But certainly Mr. Camp- 

 bell had no theory ; so far is he from having 

 had a theory that he finds it extremely diffi- 

 cult, if not at present actually impossible, 

 to formulate one, which will satisfactorily 

 account for the extraordinary fact brought 

 to light by the simple arrangement of his 

 catalogue. 



Witness his words in Lick Observatory 

 "Bulletin," No. 196, dated April 20 last: 



The correct interpretation of the observed facts 

 referred to in this "Bulletin" seems not easy of 

 accomplishment, and the brief comments which 

 follow make no pretensions to the status of a 

 solution. 



That stellar velocities should be functions of 

 spectral types is one of the surprising results of 

 recent studies in stellar motions, for we naturally 

 think of all matter as equally old gravitationally. 

 Why should not the materials composing a nebula 

 or a Class B star have been acted upon as long 

 and as effectively as the materials in a Cflass M 

 star? . . . The established fact of increasing stel- 

 lar velocities with increasing ages suggests the 

 questions: Are stellar materials in the ante-stellar 

 state subject to Newton's law of gravitation? Do 

 these materials exist in forms so finely divided 

 that repulsion under radiation pressure more or 

 less closely balances gravitational attraction? 

 Does gravity become effective only after the proc- 

 esses of combination are well under way? 



Mr. Campbell is far from being helpless 

 in the situation he has created ; he is ready 

 with suggestions, though he modestly puts 

 them as questions; but they are obviously 

 consequent, and not antecedent, to the ad- 

 vance which he has made. Even if the like 

 has never happened before, this scientific 

 advance is at any rate due to little more 

 than the accumulation of facts which ar- 

 ranged themselves, as Bacon hoped would 

 naturally happen. But does it detract 

 from the merits of this fine piece of obser- 

 vational work that it was suggested by no 

 leading theory? And I will ask even 

 further : Would its merits have been less if 

 no such immediate induction had presented 

 itself? To this second question I can 

 scarcely expect a general answer in the 

 affirmative ; it is so natural to judge by re- 

 sults, and so difficult to look beyond them 

 to the merits of the work itself that I shall 

 not easilj^ carry others with me in claiming 

 that the merits of the observer shall be as- 

 sessed independently of his results. And 

 yet I affirm unhesitatingly that until this 

 attitude is reached we can not do justice 

 to the observer. I believe it will be reached 



