Are the stars subject to growth and decay? We might almost as well ask, Are they subject to the laws of nature? There can be in either case no doubt about the reply. We are perfectly assured, both from reason and revelation, that a time was when they were not, and that at some future date they will have ceased to be. And we may further confidently affirm, guided by the analogy of all other creative processes with which we are acquainted, that their present condition has been gradually attained and will gradually become modified.

Each has then a life-history. It is what it is, because it has been what it was. Nor is it conceivable that all should have arrived simultaneously at the same stage of development. A contemporaneous universal origin can by no means be assumed as a postulate; and even if it could, the rate of progress of individual stars must have been indefinitely varied. There is hence a strong probability that the present state of some represents the past of others, the future of many more. Among the hosts of heaven we may expect to find stars in embryo, stars half formed yet chaotic, full-grown stars in orderly and equable working order, stars still effective as radiators though of declining powers, and stars on the verge of decrepitude. Their comparative study ought then, under certain conditions, to enable us to compile, as it were, the typical biography of an average star.