Page:The Natural History of Pliny.djvu/88

 54 plint's NATTJEAL HISTOET. [Book II. and tlience to the sun of 500,000,000 ^ It is in consequence of 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 follow, 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- miUia." 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. of the sun'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 in the same proportion.
 * The words in the text are "vicies centum millia" and "quinquies
 * The author's reasoning is foimded upon the supposition of the length