Appendix. Ixxi 



will provide, a boundless field for research and for exercise of the 

 highest efforts of the human intellect. 



Sixty years ago no one believed it possible that astronomy 

 could embrace the study of the constitution as well as the 

 motions of celestial objects. It is true that the speculations of 

 Laplace seemed so well based, and to fit so well with known 

 facts and scientific possibilities, as to afford the belief that the 

 sun and planets had been evolved from common primordial 

 matter. But Laplace's views could only be regarded in the light 

 of a hypothesis ; they were not capable of that proof which 

 is necessary to raise speculation, however plausible, to the level of 

 scientific truth. Comte, in his '' Cours de Philosophic Positive," 

 expressed the opinion of his time thus : "We may speculate with 

 some hope of success on the formation of the Solar System of which 

 we form a part, for it presents to us numerous perfectly well-known 

 phenomena, susceptible perhaps of giving proof of its true immediate 

 origin. But what, on the other hand, could possibly form a rational 

 basis for our conjectures on the formation of other suns ? How 

 confirm or disprove by the evidence of phenomena any cosmogonical 

 hypothesis when no phenomena of such a kind are known, nor, 

 doubtless, are even knowable?" In other words, the philosophic 

 dictum of sixty years ago was that the chemical constitution of other 

 systems than our own is a subject which, from the nature of things, 

 must be regarded as unknowable. But the discovery of the lines in 

 the Solar Spectrum by Fraunhofer, the interpretation of the meaning 

 of these lines by Kirchhoff and Bunsen, and the application of the 

 spectroscope to other celestial objects has upset that philosophic 

 conception of the unknowable, and given to us the new astronomy. 



This new astronomy deals not so much with the position as with 

 the constitution of celestial objects. Its aim is not so much to answer 

 the question where is such a star, but what is it, what can we find 

 out about its chemical constitution, and the chemical history of its 

 development ? But with all this distinctive difference between the 

 new and the old astronomy, it is impossible to divorce the one from the 

 other. There is perhaps no finer illustration of the co-relation of the 

 physical sciences than is to be found in the outcome of this new 

 development of astronomy. The old astronomy required the com- 

 bined efforts of the optician, the mechanician, the engineer, the 

 observer, and the mathematician for its pursuit, the new astronomy 

 adds those of the physicist and the chemist, and we are every day 

 finding out not only how each and all of these branches of science 

 contribute to the advancement of astronomy in general, but also how 

 their common application to astronomy has contributed to the 



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