ASTRONOMY, 
in the centre of the solar orbit, he re- 
moved it to the distance of Jjth part of 
ihe radius, and fixed the apogee to the 
sixth degree of Gemini. By means of these 
data, he formed the first solar tables of 
which any mention is made in the history 
of astronomy ; and though defective, and 
even erroneous in principle, they.are a du- 
rable monument of his genius, which three 
centuries afterwards were respected by 
Ptolemy, without his presuming to alter 
them. The great astronomer next consi- 
dered the motions of the moon, and endea- 
voured to measure the exact time of her re- 
volution, by a comparison of ancient eclipses. 
He also determined the eccentricity and in- 
clination of her orbit, as well as the motion 
of her nodes and apogee ; and calculated all 
the eclipses that were to happen for 600 
years to come. 
Between the time of Hipparchus and 
Ptolemy, the chief observers of any note 
are Agrippa, Menelaus, and Theon ; the 
two latter of which are better known as 
geometricians than astronomers. We re- 
i mark, however, in this interval, the refor- 
mation of the calendar by Julius Caesar, 
and a more exact knowledge of the flux 
and reflux of the ocean. We pass over the 
dark ages, and observe that Frederic II. 
about 1230, set himself to restore some de- 
cayed universities, and founding a new one 
at Vienna. He also caused the works of Aris- 
totle and Ptolemy’s Almagest, to be trans- 
lated into Latin; from which latter cir- 
cumstance we may date the revival of 
astronomy in Europe. Two years after 
this, John of Halifax, commonly known by 
the name of Sacro Bosco, compiled from 
Ptolemy, Albategnius, Alfraganus, and other 
Arabic astronomers, his work “ De Sphaera,” 
which continued in great estimation for 
more than 300 years afterwards, and was 
honoured with commentaries by Clavius, 
and other learned men. Alphonsus, King 
of Castile, may also be reckoned as one of 
the most zealous eucouragers and protec- 
tors of this science ; though being but ill 
seconded by the astronomers of that time, 
the tables which he published were not 
found to answer the great expense which 
attended them. See Almagest. 
About the same period also Roger Ba- 
con, an English monk, besides many learned 
works of various kinds, wrote several trea- 
tises on astronomy ; after which but little 
progress was made in the science till the 
time of Purbach, Regiomontanus, and Wal- 
ther, who all flourished about the end of 
the fifteenth century, and by their labours 
prepared the way for the great discoveries 
which followed. Regiomontanus, in parti- 
cular, who was born at Koningsberg, a 
town of Franconia, in 1426, and whose 
proper name was John Muller, rendered 
considerable services to astronomy, not 
only by his observations and writings, but 
by his trigonometrical tables of sines and 
tangents, which he computed to a radius of 
1,000,000 for every minute of the quad- 
rant, and by this means greatly facilitated 
astronomical computations. Next after 
these was Nicholaus Copernicus, the cele- 
brated restorer of the old Pythagorean 
system of the world, which had been now 
set aside ever since the time of Ptolemy. 
He was born at Thorn, in Polish Prussia, 
in 1413, and having gone through a regular 
course of studies at Cracow, and afterwards 
at Rome, he was made by the interest of 
his uncle, who was bishop of V'ormia, a 
canon of Frawenberg; in which peaceful 
retreat, after 36 years of observations and 
meditations, he established his theory of 
the motion of the earth, with, such new and 
demonstrative arguments in its favour, that 
it has gradually prevailed from that time, 
and is now universally received by the 
learned throughout Europe. This great 
man, however, had not the satisfaction of 
witnessing the success of his undertaking : 
being threatened by the persecution of reli- 
gious bigots on the one side, and with an 
obstinate and violent opposition from those 
who cailed themselves philosophers on the 
other, it was not without the greatest so- 
licitations that he could be prevailed upon 
to give up his papers to his friends, with 
permission to make them public ; but from 
continued importunities of this kind, he at 
length complied, and his book, “ De Re- 
volutionibus Orbium Coelestium,” after 
being suppressed for many years, was at 
length published, and a copy of it brought 
to him a few hours before bis death. From 
Copernicus we proceed to Tycho Brahe, 
the celebrated Danish astronomer, who 
was born in 1546, and began to manifest 
his taste for this science at the early age of 
14. An eclipse of the sun which happened 
in 1560, first attracted his attention ; and 
the justness of the calculation which an- 
nounced this phaenomenon inspired him 
with a strong desire of understanding the 
principles upon which it was founded. But 
meeting with some opposition from his 
tutor, and a part of his family, to these pur- 
, suits, which probably served only to in- 
