niversity,
and they are now liberally endowed. The University of Bologna (where,
you may remember, Copernicus learnt mathematics) has recently celebrated
its 800th anniversary.

The scientific history of the century after Newton, summarized in the
above table of dates, embraces the labours of the great mathematicians
Clairaut, Euler, D'Alembert, and especially of Lagrange and Laplace.

But the main work of all these men was hardly pioneering work. It was
rather the surveying, and mapping out, and bringing into cultivation, of
lands already discovered. Probably Herschel may be justly regarded as
the next true pioneer. We shall not, however, properly appreciate the
stages through which astronomy has passed, nor shall we be prepared
adequately to welcome the discoveries of modern times unless we pay some
attention to the intervening age. Moreover, during this era several
facts of great moment gradually came into recognition; and the
importance of the discovery we have now to speak of can hardly be
over-estimated.

Our whole direct knowledge of the planetary and stellar universe, from
the early observations of the ancients down to the magnificent
discoveries of a Herschel, depends entirely upon our happening to
possess a sense of sight. To no other of our senses do any other worlds
than our own in the slightest degree appeal. We touch them or hear them
never. Consequently, if the human race had happened to be blind, no
other world but the one it groped its way upon could ever have been
known or imagined by it. The outside universe would have existed, but
man would have been entirely and hopelessly ignorant of it. The bare
idea of an outside universe beyond the world would have been
inconceivable, and might have been scouted as absurd. We do possess the
sense of sight; but is it to be supposed that we possess every sense
that can be possessed by finite beings? There is not the least ground
for such an assumption. It is easy to imagine a deaf race or a blind
race: it is not so easy to imagine a race more highly endowed with
senses than our own; and yet the sense of smell in animals may give us
some aid in thinking of powers of perception which transcend our own in
particular directions. If there were a race with higher or other senses
than our own, or if the human race should ever in the process of
development acquire such extra sense-organs, a whole universe of
existent fact might become for the first time perceived by us