115 
earth. This problem surpassed the loftiest efforts of the 
human mind for many centuries. It was, comparatively 
speaking, easy to measure the distance of the moon and the 
nearer planets, and even the sun ; inasmuch as by simultaneous 
observation of any one of the bodies from two different points 
on the surface of the earth, and from the consequent diurnal 
parallax, its distance was easily ascertainable by a simple 
formula. But with the fixed stars this course was imprac- 
ticable ; inasmuch as the space between any two points on the 
surface of the globe is absolutely insignificant when compared 
with the tremendous depth of space which separates the earth 
from even the nearest of such stars. It was found, indeed, 
that when any fixed star was observed from one given spot, at 
intervals of six months, giving, as a base-line, the intermediate 
passage of the globe in its annual orbit round the sun ( i.e . 
about 190,000,000 miles), the most powerful telescope could 
detect no parallax. This circumstance was formerly made use 
of by astronomers, in order to throw ridicule upon the disco- 
very of Copernicus. They argued that it was impossible the 
earth could be making an annual circuit of nearly 400,000,000 
miles round the sun ; because, if so, the fixed stars must of 
course appear in different positions at different periods of the 
year. In vain did the advocates of the Copernican system 
reply, that this was caused by the prodigious distances of the 
fixed stars, which made the orbit of the earth itself, vast as it 
is, a mere speck in comparison. In their ignorance of that 
fact, many of the old philosophers still refused to believe. 
Since then, however, by means of improved telescopes, and the 
clever researches of such men as Henderson, Bessel, and others, 
the annual parallax of certain fixed stars has been discovered ; 
and, as a consequence, their actual distance from the earth. 
12. This discovery ranks among the most notable of those 
which belong to the domain of modern science, and has greatly 
added to the sublimity of our astronomical knowledge. It w r as 
between the years 1838-40 that Professor Bessel, of Konigs- 
berg obtained the most unequivocal results in this matter. I 
say unequivocal, because all astronomers concur in regarding 
his calculations as correct. The parallax which Bessel deter- 
mined was that of the double star 61 Cygni, amounting only 
to OBIS", or to very little more than a third of a second of 
space ; from which it w r as soon calculated that the distance of 
this star from our earth must be such that light (which is 
Known to travel at the rate of 192,000 miles per second) must 
take 9£ years to pass from it to us. 
13. It may serve to give some idea of the immense distances 
of the main mass of the fixed stars when we say that only nine 
