[63e]
and the” above with the above, we shall discover that these all become and are opposite and oblique and in every way different in their mutual relations. There is, however, this one fact to be noticed about them all, that it is the passage of each kind to its kindred mass which makes the moving body heavy, and the region to which such a body moves “below”; while the opposite conditions produce the contrary results.1 Let this, then, stand as our account of the causes of these conditions.
Of “smoothness” and “roughness” anyone might be able to discern the causes and explain them also to others. For the cause of the latter is hardness combined with irregularity, and of the former
