ir 
THE 
LONDON, EDINBURGH axv DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[THIRD SERIES.} 
FEBRUARY 1843. 
XIII. On the Constitution of the Sidereal System, of which 
the Sun forms a part. ByO.¥. Mossorti, Professor of 
Pure and Applied Mathematics in the University of the 
Lonian Islands*. 
STRONOMY, as if sensible of the smallness of the being 
that was creating it, was very slow and backward in dis- 
covering the immensity of the field that lay open to its inves- 
tigations. The first astronomers, believing the earth to be 
immoveable in the centre of the universe, did not dare to ex- 
tend the limits of the heavenly vault beyond a million of geo- 
graphicai miles. When the Pythagorean school gave forth 
the bold conception, that the earth was a planet revolving 
round the sun, it became necessary to consider the radius of 
the earth’s orbit as of insensible magnitude with regard to 
that of the celestial sphere, and Aristarchus of Samos (who 
had adopted the ideas of the Pythagorean school) increased 
the radius of the latter six hundred and thirty-five times f. 
The limits of the universe are however infinitely more re- 
mote: the depth of the heavens confounds itself with the im- 
mensity of space. In the last century astronomers determined 
with precision the distance that separates us from the sun, 
and, what is no less wonderful, the rapid velocity with which 
light is propagated. The eighty-two millions and two-thirds 
of a million of miles between the earth and the sun are tra- 
versed by light in the short time of eight minutes and thirteen 
seconds. Now, according to the recent accurate calculations 
* Extracted from an Introductory Lecture delivered by the Author on 
the 1st of October 1839, at the opening of the University Session: printed 
at Corfu in 1840. Translated from the Italian, and communicated at the 
request of the Author, by E, H. J. Craufurd, B.A., Trin. Coll. Cambridge. 
t Arist. Sam. de magnit. et dist. Solis et Lun. Edit. 1572. in 4to, Pappus 
Coll. Mathem., lib. vi. prop. 38. Archimedes in Arenario, 
Phil. Mag, 8.3. Vol. 22. No. 143. Feb. 1843. G 
