Centimillennium

A Millennium consists of one thousand years. / A Decamillennium is ten thousand years. /[…]/ A Centimillennium embraces a period of one hundred thousand years.

After that the land was quiet for a long time, and the decimillennia passed and ran on into centimillennia, and the centimillennia piled up into millionennia.[…]And, as the centimillennia passed, the hills grew lower still and the valleys broader, so that the whole land was only of a rolling surface, as if it would soon be a plain.

To dig down through the layers of anthropology, to compare spokeshave and arrowhead, awl and drill – embedded codices – from the abandoned shelters of the earth, to hobnob with millennia and to quote centimillennia with the same sort of respect as was previously accorded to the aristocracy, is to cite the modern quality.

This suggests, for one thing, that if our Australopithecoid ancestry possessed a brain-volume approximating that of a chimpanzee, in the late Tertiary, an additional 2 mitotic divisions over a period of some centimillennia would really not suggest that the human capacity is the product of an ‘explosion of brains’ under a terrific ‘selective pressure’, — as appears to be a current view of the matter.

A lot of this book dealt with long periods of time. I coined words in there. There was no unit of time longer than a millennium in ordinary usage, which doesn't do at all. So I coined "decimillennium" and "centimillennium," and I used "millennium" for a million years. I doubt if you'd find those anywhere else, but it's pretty obvious what they mean. I really needed them in this book, because I was dealing in periods very much longer than a thousand years.

Do the millennia and the centimillennia dash between us and this dream? Must the sun be extinguished and reignited a thousand times?

I see no reason not to consider Jackson the text of choice for the next millennium, or at least the next centimillennium.