1912] The Ottawa Naturalist. 33 



closely in position with the unknown bright lines in the nebular 

 spectrum. We seem to be. with all the recent developments in 

 radio-activity and the ultimate constitution of matter, on the 

 eve of most important discoveries and generalizations not onlv in 

 astronomy but in its sister sciences, physics and chemistrv. 

 Notwithstanding the diversity of composition indicated, it is 

 believed that all these bodies contain the same elements, our 

 terrestrial substances, and that only the spectra of .the elements 

 appear which are most easily produced by the particular forms 

 of energy in action. It is not probable that the luminositv is 

 produced by heat, for the enormously extended and attenuated 

 matter of the nebulae must be at a very low temperature; 

 it is rather a sort of luminescence, perhaps due to electrical 

 action or to some form of radio-aetivitv. 



We have in the nebulae, according to the practicallv 

 universal belief of scientific men, the primal form of matter, 

 the material from which suns and w r orlds are made. From this 

 world stuff, if I may use the term, we can trace the evolution, 

 following simple and well known laws, to suns and stars in all 

 their stages, to planets, comets and all the heavenly host. Fur- 

 ther than this also, though this is the province more particularly 

 of your science, following also other simple and well known 

 laws, the gradual development of life on planets such as ours 

 from the lower to the higher forms can equally well be traced. 



In the tracing of this evolution in the heavens, it must 

 not be for a moment supposed that it can be followed .in any 

 one star, any more than that the changes in living organisms 

 can be detected in one generation. Stellar development is so 

 inconceivably slow that it is very doubtful whether any change 

 could be detected in a million years. But we have in the sky 

 so rich a field for observation, such a great number of stars in 

 all stages of their development, that by the aid of the spectroscope 

 and by data obtained in numerous other ways it is possible to 

 arrange in orderly sequence the process of evolution. If we 

 suppose ourselves in an oak forest, though we could not 

 expect to see the growth of any one oak from the acorn and seed- 

 ling through small and large to a fully developed tree, and then 

 through the process of decay to a crumbling log, vet we would 

 have no difficulty, owing to the examples in all stages of growth 

 around us, in correctly tracing and arranging the. development. 



Let us begin then with our nebula, whether gaseous or of 

 finely divided particles does not matter, as, by the theory of 

 the chemical unity of the cosmos, there are all the terrestrial 

 elements present or perhaps, to be more precise, at least 

 matter out of which all terrestrial elements mav appear. It is 

 practically certain that this matter is extremelv attenuated or 



