ALEXANDRIAN OR HELLENISTIC PERIOD 



to have reached so remarkable a conclusion, we have 

 to some extent guessed at the processes of thought- 

 development ; for no line of explication written by the 

 astronomer himself on this particular point has come 

 down to us. There does exist, however, as we have I 

 already stated, a very remarkable treatise by Aris-l 

 tarchus on the Size and Distance of the Sun and the 

 Moon, which so clearly suggests the methods of 

 reasoning of the great astronomer, and so explicitly 

 cites the results of his measurements, that we cannot 

 well pass it by without quoting from it at some length. 

 It is certainly one of the most remarkable scientific 

 documents of antiquity. As already noted, the 

 heliocentric doctrine is not expressly stated here. 

 It seems to be tacitly implied throughout, but it is 

 not a necessary consequence of any of the propositions 

 expressly stated. These propositions have to do with 

 certain observations and measurements and what 

 Aristarchus believes to be inevitable deductions from 

 them, and he perhaps did not wish to have these 

 deductions challenged through associating them with 

 a theory which his contemporaries did not accept. 

 In a word, the paper of Aristarchus is a rigidly scien- 

 tific document unvitiated by association with any 

 theorizings that are not directly germane to its central 

 theme. The treatise opens with certain hypotheses 

 as follows : 



"First. The moon receives its light from the sun. 



"Second. The earth may be considered as a point 

 and as the centre of the orbit of the moon. 



"Third. When the moon appears to us dichotomized 

 it offers to our view a great circle [or actual meridian] 



221 



