GRAVITATIONAL MOTION 199 



motion are quite dissimilar, at least in the sense that the first 

 is that of a continuous medium in direct contact with its dis- 

 turbing force, while the second is that of an object obviously 

 separated from its mover, one should not make too much of 

 this argument, but there does seem to be a suggestion here 

 of some motive power being communicated to parts of the 

 fluid and thus accounting for its continued motion. 



In discussing the motions of fluids considered as wholes, such 

 as winds, clouds, mists, rain, etc., Theodoric develops this 

 notion further. He considers these as " incomplete entities not 

 yet separated from their generator," and maintains that they 

 have some motive principle, apart from the intrinsic gravi- 

 tational principle associated with their elemental constituents, 

 by which they fulfill a particular end intended by nature.-^ 

 The gravitational principle, he notes, is analogous to the intrin- 

 sic principle that might be induced into a body by the action 

 of an altering agent, and here he gives the interesting example 

 of a magnet's action on iron, which he observes causes the 

 iron " to tend towards it in a straight line wherever it might 

 be, whether through air, water, or a metallic container 



" 24 



violentam alterius partis impulsionem vel aUractionem, motu suo natural! redeunt 

 rursum ad locum suum proprium et ipse tales partes et impellentes. Et sic per talem 

 impulsionem, tractionem parclum, subinteraccionem, fit quedam inundacio talis 

 corporis humidi in suis partibus. Quo fit eciam ut non statim cesset huiusmodi 

 motus ad cessacionem primi moventis primam partem, quia sicut dictum est huius- 

 modi motus componitur ex naturali et violento, qui ex disposicione sibi, ex mutua 

 disposicione seu alteracione vel influencia indita, sepius super seinvicem replicantur, 

 cum in huiusmodi naturalis motus sequatur violentum, et violentus causetur a 

 naturali. 



"■" Cap. 15, M 15rb, U 142rb. 



-* Cap. 16, M 15va, U 142va-b: Et huiusmodi motus per naturam non solum 

 competit rebus que moventur ad aliquem naturalium locorum mundi secundum 

 determinatam habitudinem ad centrum et circumferenciam mundi, et hoc secundum 

 aliquod principium inexistens per mocionem generantis, sed ' eciam sic moventur 

 secundum naturam principii inexistentis per approximacionem alicuius corporis 

 alterantis seu aliquo modo afficientis ea. Cuiusmodi est motus ferri ad magnetem, 

 quod non impeditum, secundum lineam rectam tendit ad ipsum ubicumque fuerit, 

 sive per aerem, sive per aquam, sive per vasa metallina, ut patet ad sensum. Sic 

 patet de quibusdam compositis qua racione moventur per naturam motu recto, quia 

 scilicet moventur per principium intrinsecum. 



