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SCIENCE 



[N. S. Vol. XXX. No. 760 



dulged in which implied that the spiral nebulae 

 are true nebulae condensing into systems of stars. 

 Though this premature and unauthorized line of 

 thought has been extensively exploited, and even 

 given place in one treatise on geology, it has 

 always seemed to the writer quite unsound. I 

 have consistently held that so far we do not know 

 the true character of the spiral nebulae, and this 

 position is amply justified by the penetrating 

 remarks of M. Poinearg. Whether the spiral neb- 

 ulae are other Milky Ways, as suggested by the 

 illustrious French geometer, time alone can tell; 

 and it may be several centuries before this ques- 

 tion can be satisfactorily settled. Meanwhile the 

 exploitation of the spiral form as typical of neb- 

 ular development is certainly misleading, for, as 

 Poinoarfi points out, there is no proof that these 

 spirals are true gaseous nebulae. 



The speculations on spiral nebulae have been 

 decidedly overdone, and it Is time to call a halt. 

 There is not the slightest probability that our 

 solar system was ever a part of a spiral nebula, 

 and such a suggestion is simply misleading and 

 mischievous. The great circularity of the planet- 

 ary orbits shows the absurdity of such an hy- 

 pothesis. . . . Least of all can we expect any light 

 from the much .exploited spiral nebulae, which as 

 M. Poincarg justly remarks, may be other galaxies. 

 It is time, therefore, to drop such spirals from 

 our text-books, or to candidly admit that we are 

 quite in the dark as to their true significance. 



In the last paper of See recently published 

 in the Astronomische NachricMen and several 

 other places we read: 



The solar system was formed from a spiral 

 nebula, revolving and slowly coiling up under 

 mechanical conditions which were essentially free 

 from hydrostatic pressure. And spiral nebulae 

 themselves arise from the meeting of two or more 

 streams of cosmical dust. The whole system of 

 particles has a sensible moment of momentum 

 about some axis, and thus it begins to whirl about 

 a central point, and gives rise to a vortex. In the 

 actual universe the spiral nebulae are to be counted 

 by the million, and it is evident that they all 

 arise from the automatic winding up of streams 

 of cosmical dust, under the attraction of their 

 mutual gravitation. . . . When the nebula rotates 

 and the coils wind up in such a way as to leave 

 open spaces between the coils, or at least freedom 

 from sensible hydrostatic pressure, the usual re- 

 sult is the development of a system made up of 

 small bodies, such as the planets compared to the 



greatly preponderant sun, or the satellites com- 

 pared to the much greater planetary masses which 

 control their motions. In the solar system where 

 the conditions are accurately known this is proved 

 to have occurred; and it was repeated so many 

 times always witli uniform results giving a large 

 central mass and small attendant bodies that the 

 general law for this condition is clearly es- 

 tablished. 



Thus we see the variety of " consistent " 

 conclusions recently reached by the twenty- 

 five years of uninterrupted work on this sub- 

 ject. 



At the end of this paper See admits its 

 value in the following modest terms : 



It has seemed advisable to call attention to the 

 cause of the roundness of the orbits of the 

 planets and satellites, because it appears likely 

 that the criteria now introduced may go far to- 

 wards clearing up the mystery which has always 

 surrounded the origin of our solar system. 



In See^s paper there are only two points of 

 divergence from the ideas fully developed by 

 Professor Chamberlin and myself. The first 

 is that spiral nebulas have their origin in 

 " the meeting of two or more streams of 

 cosmical dust." The second is that satel- 

 lites are captured bodies. This latter view has 

 been advanced by many amateurs and a 

 few astronomers. It was considered in my 

 writings quoted above, and rejected for what 

 seemed to me to be good reasons. The resist- 

 ing medium on which so much stress is laid is 

 simply a special case of the collisions of any 

 character considered by Professor Chamber- 

 lin and myself. 



The quotations above are sufficient to re- 

 move the clouds which See's pretensions of long 

 study of, and valuable contributions to, this 

 subject might raise in the minds of those not 

 particularly familiar with the history of 

 recent developments in cosmogony. I wish 

 to point out that notwithstanding the evi- 

 dence furnished by his 1906 paper of his 

 familiarity with our work, and in spite of the 

 fact that at his request I furnished him re- 

 prints of my papers several months in ad- 

 vance of his recent publication, there is in it 

 no direct or indirect reference to Professor 



