The Adolfo Stahl lectures in astronomy, delivered in San Francisco, California, in 1916-17 and 1917-18, under the auspices of the Astronomical Society of the Pacific (1919)
Astronomical Society of the Pacific, Aitken, Robert Grant, 1864-1951 · San Francisco Stanford University Press · leaf 60
he head of a comet could happen, but we see no reason toquestion the accuracy of the estimates made by mathematicalastronomers that such encounters will not occur more thanonce in fifteen or twenty million years, on the average! It is byno means certain that such an encounter, should one everoccur,… … PLATE \l. Halleys Comet, May 1. 1910: Head axd Beginning OF Tail. Photograph by H. D. Curtis. What We Know About Comets 27 are of the opinion that the outcropping strata of the Earthwhich they have been able to study have required a period ofapproximately one hundred million years for their…
Astronomy
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
