Page:Popular Science Monthly Volume 82.djvu/595

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Another source of evidence for the evolution of organisms is that derived from the study of paleontology; for the successive geological strata constitute a record of the organic forms which have successively inhabited the earth; a record which shows that in all the forms of life there is a considerable degree of continuity, and a (more or less) gradual transition from one form to another.

The homologue of this geological record in inorganic evolution is to be found in the series of stars arranged in order of decreasing temperature; for what the unknown cause of organic evolution has done for organisms, leaving the record in the geological formations, temperature (and perhaps other agencies) have done for the elements, leaving the record in stars of different heat intensities.

Lockyer has shown that the spectroscopic study of the stars, as carried on by himself and others, has revealed evidence of a very important kind for inorganic evolution. Here the results can only be briefly indicated.

As pointed out by Sir Norman Lockyer, the simplest elements appear first.

The stellar evidence, like the geological record, is incomplete, because, as stated by Lockyer, of the very small range of the photographs of stellar spectra, and also because

But whatever has been gleaned from the stellar evidence, though incomplete, is, like the information contained in the geological record, very significant in its indications of evolution.