birth-time of the world and whether likewise there is to be any
end." "And if" (he says in answer) "there was no birth-time of
earth and heaven and they have been from everlasting, why before
the Theban war and the destruction of Troy have not other poets
as well sung other themes? Whither have so many deeds of men so
often passed away, why live they nowhere embodied in lasting
records of fame? The truth methinks is that the sum has but a
recent date, and the nature of the world is new and has but
lately had its commencement."[2]

Thus spake Lucretius nearly 2,000 years ago. Since then we have
attained another standpoint and found very different limitations.
To Lucretius the world commenced with man, and the answer he
would give to his questions was in accord with his philosophy: he
would date the birth-time of the world from the time when

[1] A lecture delivered before the Royal Dublin Society, February
6th, 1914. _Science Progress_, vol. ix., p. 37

[2] _De Rerum Natura_, translated by H. A. J. Munro (Cambridge,
1886).

1

poets first sang upon the earth. Modern Science has along with
the theory that the Earth dated its beginning with the advent of
man, swept utterly away this beautiful imagining. We can, indeed,
find no beginning of the world. We trace back events and come to
barriers which close our vista--barriers which, for all we know,
may for ever close it. They stand like the gates of ivory and of