ASTRONOMY. 341 



it was, was adopted and generally admitted, for the space of fourteen 

 centuries, during which time, it was transmitted to the Arabs, the 

 Persians, arid the Indians, with whom it is still held sacred. 



To this celebrated Grecian we also owe the substitution of the Sines 

 sines of arcs instead of their chords ; as also the first enumeration of SnJ 

 some important theorems in trigonometry. 



Ptolemy was the author of that system of astronomy which still Ptolemy's 



, , . -r i v i ." i L ' f ji arguments 



bears his name ; or, it he did not entirely invent it (as there is great to prove the 

 reason to suppose he did not), he enforced it by such arguments as led immobility ' 

 to its establishment ; and it was afterwards rendered sacred through the 

 stupid bigotry and intolerance of the Romish church. He endeavours 

 to prove the absolute immobility of the earth, by observing, " If the 

 earth had a motion of translation common to other heavy bodies, 

 it would, in consequence of its superior mass, precede them in space, 

 and pass even beyond the bounds of the heavens, leaving all the 

 animals and other bodies without any support but air ; which are 

 consequences to the last degree ridiculous and absurd." In the same 

 place he adds, " Some persons pretend, that there is nothing to 

 prevent us from supposing that the heavens remain immoveable, while 

 the earth turns on its own axis from west to east, making this revo- 

 lution in a day nearly ; or that, if the heavens and the earth both 

 turn, it is in a ratio corresponding with the relations we have observed 

 between them. It is true, that as to the stars themselves, and con- 

 sidering only their phenomena, there is nothing to prevent us, for the 

 sake of simplicity, from making such a supposition. But these people 

 are not aware how ridiculous their opinion is, when considered with 

 reference to events which take place about us; for if we concede to 

 them that the lightest bodies, consisting of parts the most subtle, are 

 not possessed of levity (which is contrary to nature), or that they 

 move not differently from bodies of a contrary kind (although we 

 daily witness the reverse) ; or, if we concede to them that the most 

 compact and heaviest bodies possess a rapid and constant motion of 

 their own (while, it is well known, that they yield only with difficulty 

 to the impulses we give to them), still, they would be* obliged to 

 acknowledge, that the earth, by its revolution, would have a motion 

 more rapid than any of those bodies which encompass it, in con- 

 sequence of the great circuit through which it must pass in so short 

 a period ; wherefore such bodies as are not supported on it, would 

 always appear to possess a motion contrary to itself; and neither 

 clouds, nor any projected bodies, nor birds in flight, would ever 

 appear to move towards the east; since the earth, always preceding 

 them in this direction, would anticipate them in their motion; and 

 everything, except the earth itself, would constantly appear to be 

 retiring towards the west." 



If we did not feel convinced that, in certain cases, even the errors 

 and false reasoning of such a man as Ptolemy, possess a greater 

 interest than the more correct and refined arguments of minor 



