54 PLrSTT's NATTJEAL HISTOET. [Book II. 



and tlience to the sun of 500,000^000 ^ It is in consequence 

 o£ this space that the sun, notwithstanding his immense 

 magnitude, does not burn the earth. Many persons have 

 imagined that the clouds rise to the height of 900 stadia. 

 These points are not completely made out, and are dif&cult 

 to explain ; but we have given the best account of them that 

 has been published, and if we may be allowed, in any degree, 

 to pursue these investigations, there is one infallible geome- 

 trical principle, which we cannot reject. Not that we can 

 ascertain the exact dimensions (for to profess to do this 

 would be almost the act of a madman), but that the mind 

 may have some estimate to direct its conjectures. Now it is 

 evident that the orbit through which the sun passes consists 

 of nearly 366 degrees, and that the diameter is always the third 

 part and a little less than the seventh of the circumference^. 

 Then taking the half of this (for the earth is placed in the 

 centre) it will foUow, that nearly one-sixth part of the im- 

 mense space, which the mind conceives as constituting the 

 orbit of the sun round the earth, will compose his altitude. 

 That of the moon will be one-twelfth part, since her course 

 is so much shorter than that of the sun ; she is therefore 

 carried along midway between the sun and the earth ^. It 

 is astonishing to what an extent the weakness of the mind 

 will proceed, urged on by a little success, as in the above- 

 mentioned instance, to give full scope to its impudence ! 

 Thus, having ventured to guess at the space between the sun 

 and the earth, we do the same with respect to the heavens, 

 because he is situated midway between them ; so that we may 

 come to know the measure of the whole world in inches. 

 Por if the diameter consist of seven parts, there will be 

 twenty-two of the same parts in the circumference ; as if we 

 could measure the heavens by a plumb-line ! 



The Egyptian calculation, which was made out by Petosi- 



1 The words in the text are " vicies centum millia " and " qninquies 

 milUa." 



2 Archimedes estimated that the diameter of a circle is to its circum- 

 ference as 1 to 3-1416 ; Hutton's Diet, in loco. Ptolemy states it to be 

 precisely as 1 to 3 ; Magn. Const, i. 12. 



3 The author's reasoning is foimded upon the supposition of the length 

 of the Sim's path round the earth being twelve times greater than that 

 of the moon's ; the orbit therefore would be twelve times greater and the 

 radius ia the same proportion. 



