JEANS was knighted in 1928 for his services to science and to the Royal Society, and it is noteworthy that this honour came to him before the publication of any of his popular books. To this phase of Jeans's life we now come.

Astronomy and Cosmogony (1928) concluded with a very moving chapter, in which Jeans summed up, without mathematics but with some vivid diagrams, his life-work of research in the ‘natural history’ of the astronomical formations—galaxies, stellar clusters, nebulae, stars (simple, double and multiple), Cepheids, novae and solar systems—which appear to constitute the material universe. The three concluding paragraphs of this chapter may be quoted in extenso:

The cosmogonist has finished his task when he has described to the best of his ability the inevitable sequence of changes which constitute the history of the material universe. But the picture which he draws opens questions of the widest interest not only to science, but also to humanity. What is the significance of the vast processes it portrays? what is the meaning, if any there be which is intelligible to us, of the vast accumulations of matter which appear, on our present interpretations of space and time, to have been created in order that they may destroy themselves? What is the relation of life to that universe of which, if we are right, it can occupy only so small a corner? What if any is our relation to the remote nebulas, for surely there must be some more direct contact than that light can travel between them and us in a hundred million years? Do their colossal incomprehending masses come nearer to representing the main ultimate reality of the universe, or do we? Are we merely part of the same picture as they, or is it possible that we are part of the artist? Are they perchance only a dream, while we are brain-cells in the mind of the dreamer? Or is our importance measured solely by the fractions of space and time we occupy—space infinitely less than a speck of dust in a vast city, and time less than one tick of a clock which has endured for ages and will tick on for ages yet to come?