andjhewn inconclusive. 285

k XX. Moreover, What a fine branch ofQ wledge have we concerning extended andlifting quantity, or body? The shock of bo-es against each other, particularly of ela-s bodies-, their perpendicular and inclinede J Cc nts 3 their motion, circular, or in otherCllr ves ; their centrifugal forces ; their centers^gravity, oscillation or percussion? Whatand surprising theorems, concerning°tfie$ moving in, or supported by jhiids %

. hese truths have still nothing for their ob-Our ideas are not heavy, resisting,^ ro jechle, fluid ; capable of being comprejf-or dilated-, have no properties of inflexi-\ refraction, &c. To allow that our i-ae as had any of these properties, would beto allow them to be solid, resisting, figur-divisible things. And to fay it is im-possible there can be any fubflance of which, are properties; or to doubt only of■ s ; is to doubt if several useful truthsnot be found out, and demonstrationsabout nothing. Let me astc, whatlnd of philosophy would such propositionsas these make ; the centrifugal forces oftlV ° e ^ual ideas, revolving in the same time,