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SCIENCE 



[N. S. Vol. LII. No. 1334 



izations of galaxies, say super-galaxies, and 

 still higher organizations of super-galasies, and 

 so on without limit. To be sure this is mere 

 speculation and rests upon no direct physical 

 evidence. But let us not forget that even in 

 the days when the atom was our smallest 

 physical unit there were many men who re- 

 fused to regard it as such upon grounds which 

 were purely metaphysical. The mere fact that 

 the physicists have been able to take one more 

 step down the series by conquering the extra- 

 ordinary experimental difficulties, and that the 

 astronomers in their turn are beginning to 

 perceive in the spiral nebulae other galaxies 

 than our own is quite encouraging to the 

 purely metaphysical notion that the series of 

 physical imits is an unending one, without 

 bottom and without top. 



Thus we have a conception of an infinite, 

 three-dimensional continuum of space about 

 which we can move at will, at least within 

 certain limits; a conception of an infinite 

 one-dimensional continuum of time through 

 which we move always in one direction, with- 

 out choice on our part; and finally, a con- 

 ception of an infinite one-dimensional series 

 of physical units in which our position is 

 fixed— it is only in thought that we can move 

 along this series. If to these we add energy 

 and consciousness, neither of which admit the 

 notion of dimensions, we have perhaps ex- 

 hausted the category of fundamental con- 

 ceptions. 



The physicists and astronomers have noth- 

 ing to do with consciousness objectly. They 

 are interested only in the conceptions of 

 space, time, the series of physical units, and 

 energy. In particular, they are interested in 

 the properties of the physical units, the nature 

 of their wonderful organizations and the flow 

 of energy which is associated with them. 

 The astronomers, fortunately, are able to 

 furnish us with photographs of the objects 

 with which they deal, so that we are able to 

 study them more or less thoroughly one at a 

 time. E"o two of the galaxies are alike in 

 detail although in their broad outlines 

 there are striking similarities. The globular 

 cluster is one type of organization of which 



we have some eighty specimens, and the 

 spiral cluster is another, and of these we 

 have some hundreds of thousands. 



Descending from the galaxies to the stars 

 we are unable to make out the structural de- 

 tails notwithstanding their vast size, owing to 

 their still more vast remoteness. Only one 

 specimen, our ovrai sun, is sufficiently friendly 

 to submit to anything like a close inspection. 

 Nevertheless a classification of the stars ac- 

 cording to their colors and their types of 

 spectra is entirely possible. Thus the in- 

 herently brilliant white Orion-type stars have 

 continuous spectra, save for a few broad lines 

 of absorption due to helium and hydrogen, 

 with a complete absence of the metallic lines. 

 The brightest part of the spectrum is in the 

 violet. Then come the stars of the solar type 

 with the yellow as the brightest part of the 

 spectrum, with many lines of hydrogen and 

 the metals. Then the orange stars with 

 metallic lines and absorption bands due to 

 chemical compounds. Finally, the deep red 

 stars with heavy absorption bands due to 

 carbon compounds. The individualities of the 

 stars, however, are preserved for no two of 

 the spectra are exactly alike. 



Nothing need be said with respect to 

 ordinary masses, for they are matters of our 

 everyday experience. No two leaves even 

 from the same tree are exactly alike. But 

 when we descend to the stage of the molecules 

 the situation is very different. The phys- 

 icists have not yet given us any photographs 

 of them to study, and no one can say that he 

 has ever seen a molecule. Their numbers are 

 so amazingly great that an individual study 

 of them is quite out of the question. Never- 

 theless, as the chemists assure us, classifica- 

 tion is quite possible, and their variety is 

 astonishingly great. But when we study the 

 properties of even a single variety and at- 

 tempt to work out their structural organiza- 

 tions we must not forget that it is only the 

 properties common to large numbers which 

 stand out and characterize the variety. If 

 the human race could be studied only through 

 the statistics of population, we might arrive 

 at the conclusion that the Chinese are a 



