DECEMBER 29, 1899.] 
‘toric extension of the universe, and the 
unity of the universe. 
The development of the idea of the ex- 
tension of the universe in space belongs 
mainly to earlier times than ours. The 
‘Greek geometers acquired approximately 
correct notions of the size of the earth and 
the distance of the moon. The Copernican 
astronomy in the sixteenth century shifted 
the center of the solar system from the earth 
to the sun, and placed in truer perspective 
our view of the celestial spheres. But, 
though astronomy, the oldest of the sister- 
hood of the sciences, attained a somewhat 
mature development centuries ago, it has 
in our own century thrown new light upon 
the subject of the vastness of the universe. 
The discovery of Neptune has greatly in- 
-ereased the area of the solar system; the 
measurement of the parallax of a few of 
the brightest and presumably the nearest 
of the stars has rendered far more definite 
our knowledge of the magnitude of the 
stellar universe ; and telescopes of higher 
magnifying power than had been used be- 
fore have resolved many clusters of small 
-and distant stars. 
If the development of the idea of the 
spatial extension of the universe belongs 
mainly to an earlier period, the idea of its 
historic extension belongs mainly to our 
-century. It is true, indeed, that Pythago- 
ras and others of the ancient philosophers 
did not fail to recognize indications of 
change in the surface of the earth. And, 
in the beginning of the Renaissance, we 
find Leonardo da Vinci and others insist- 
ing that the fossils discovered in excava- 
tions in the stratified rocks were proof of 
the former existence of a sea teeming with 
marine life, where cultivated lands and 
populous cities had taken its place. Hut- 
ton’s ‘Theory of the Earth,’ which in an 
important sense marks the beginning of 
modern geological theorizing, appeared in 
the Edinburgh Philosophical Transactions in 
SCIENCE. 
947 
1788, but was not published a sa separate 
work till seven years later. Not till 1815 
was published William Smith’s Geological 
Map of England, the first example of sys- 
tematic stratigraphic work extended over 
any large area of country. To the be- 
ginning of our country belong also the 
classical and epoch-making researches of 
Cuvier upon the fossil fauna of the Paris 
basin. By far the larger part, therefore, of 
the development of geologic science, with 
its far-reaching revelations of continental 
emergence and submergence, mountain 
growth and decay, and evolution and ex- 
tinction of successive faunas and floras, be- 
longs to the nineteenth century. Far on 
into our century extended the conflict with 
theological conservatism, in which the elder 
Silliman, James L. Kingsley, and others of 
the early members of our Academy bore an 
honorable part, and which ended in the 
recognition, by the general public as well as 
by the select circle of scientific students, of 
an antiquity of the earth far transcending 
the limits allowed by venerable tradition. 
To our century also belongs chiefly the 
development in astronomy of the idea of 
the history of the solar system. It is, 
indeed, true that, in the conception of 
the nebular hypothesis, Laplace, whose 
“Théorie de la Monde’’ was published in 
1796, was preceded by Kant and Sweden- 
borg; yet the credit of the discovery be- ° 
longs not so much to the first conception of 
the idea as to its development into a thor- 
oughly scientific theory. Our century, 
moreover, has added to those evidences of 
the nebular theory, which Laplace derived 
from the analogies of movement in the 
solar system, the evidence furnished by the 
spectroscope, which finds in the nebulae 
matter in some such condition as that from 
which the solar system is supposed to have 
been evolved. 
But by far the most important contribu- 
tion of this century to the intellectual life 
