390 
difference in the computed time for the occultation of Jupiter’s 
satellites when that planet is nearest and when it is most 
distant from the earth. And when the earth's distance from 
the sun was regarded as 95 millions of miles, the velocity of 
light so calculated was regarded as 192,000 miles per second, 
but has since been reduced by 8,000 miles per second, or to 
183,470 miles, when the earth's distance from the sun was 
reduced six years ago to 91 million miles.* I must refer to 
what I have pointed out elsewhere as to the supposed experi- 
mental verifications of each of these astronomical rates, by 
Helmholtz and Foucault respectively, with an accuracy in the 
former instance, it was said, “ to the 77-millionth part of a 
second ! 33 f And I only allude to this here that it may be kept 
in mind that it is to our theoretical and physical Astronomy, 
and not to Optics, that we owe our modern teaching as to the 
velocity of light, as well as those curious speculations which 
have been based upon it relating to the fixed stars. 
22. But now I must notice that our modern astronomers, 
having further discovered that the so-called “ fixed stars 33 are 
not literally all fixed in the sense that earned them that ap- 
pellation, have further illogically deduced from what is called 
the “ proper motions 33 of some such stars the theory of “ solar 
motion in space." I ought to state, however, that the notion 
of the fixed stars not being really ’fixed, or immovable with 
respect to each other, was actually put forward as a specula- 
tion “ before the observations of astronomers acquired a 
sufficient degree of precision to indicate even the slightest 
trace of its real existence." J One of the first persons to 
make this guess was Jordano Bruno, formerly a Dominican 
monk, who seems to have renounced the religious extra- 
vagances, first of Home and then of Geneva, only to launch 
into other extravagant speculations of his own. But of his 
sincerity there can be no doubt. He was imprisoned by the 
Inquisition for two years, and was burnt as a heretic and an 
infidel in the year 1600. But Halley is said to have been 
the first who adopted the notion of the proper motion 
of the fixed stars from actual observation. § Bradley thought 
the apparent motions of some of the stars might arise, either 
from a motion of the solar system in space, or from a real 
change in the position of the stars themselves. Thomas 
Wright, of Durham (a name little known), in a book published 
in 1750, concluded “that the sun with its cortege of planets, 
as well as all the stars of the firmament, are in continual 
# Current Phys. Ast., b. iii., pp. 38-48. (Hardwicke.) 
t Vide Note A. J Grant, p. 553. § lb. 554. 
