320 LAPLACE. 
action of Saturn, forming a total of 618 days, or more 
than a year and eight months. 
Never did a question of astronomy excite a more in- 
tense, a more legitimate curiosity. All classes of society 
awaited with equal interest the announced apparition. 
A Saxon peasant, Palitzch, first perceived the comet. 
Henceforward, from one extremity of Europe to the 
other, a thousand telescopes traced each night the path 
of the body through the constellations. ‘The route was 
always, within the limits of precision of the calculations, 
that which Clairaut had indicated beforehand. The pre- 
diction of the illustrious geometer was verified in regard 
both to time and space: astronomy had just achieved a 
great and important triumph, and, as usual, had destroyed 
at one blow a disgraceful and inveterate prejudice. As 
soon as it was established that the returns of comets 
might be calculated beforehand, those bodies lost for ever 
their ancient prestige. The most timid minds troubled 
themselves quite as little about them as about eclipses of 
the sun and moon, which are equally subject to calcula- 
tion. In fine, the labours of Clairaut had produced a 
deeper impression on the public mind than the learned, 
ingenious, and acute reasoning of Bayle. 
The heavens offer to reflecting minds nothing more 
curious or more strange than the equality which subsists 
between the movements of rotation and revolution of our 
satellite. By reason of this perfect equality the moon 
always presents the same side to the earth. The hemi- 
sphere which we see in the present day is precisely that 
which our ancestors saw in the most remote ages; it is 
exactly the hemisphere which future generations will 
perceive. 
The doctrine of final causes which certain philosophers 
