640 . HOVUM ORGAKtJM. [bOOK tl 



different parts urging trie otlier in succession, tLe wliole is moved, 

 and that with a rotatory as well as progressive motion, in order 

 that the parts may, by this means also, set themselves at liberty, 

 or more readily submit. Let this suffice for the motion in 

 question. 



Let the fourth be that which we terra the motion of matter, 

 and which is opposed to the last ; for in the motion of liberty, 

 bodies abhor, reject, and avoid a new size or volume, or any new 

 expansion or contraction (for these different terms have the same 

 meaning), and strive, with all their power, to rebound and 

 resume their former density ; on the contrary, in the motion of 

 matter, they are anxious to acquire a new volume or dimension, 

 and attempt it willingly and rapidly, and occasionally by a most 

 vigorous effort, as in the example of gunpowder. The most 

 powerful, or at least most frequent, though not the only in- 

 struments of this motion, are heat and cold. For instance, the 

 air, if expanded by tension (as by suction in the glass egg), 

 struggles anxiously to restore itself; but if heat be applied, it 

 strives, on the contrary, to dilate itself, and longs for a larger 

 volume, regularly passing and migrating into it, as into a new 

 form (as it is termed) ; nor after a certain degree of expansion 

 is it anxious to return, unless it be invited to do so by the 

 application of cold, which is not indeed a return, but a fresh 

 change. So also water, when confined by compression, resists, 

 and wishes to become as it was before, namely, more expanded ; but 

 if there happen an intense and continued cold, it changes itself 

 readily, and of its own accord, into the condensed state of ice ; 

 and if the cold be long-continued, "without any intervening 

 warmth (as in grottos and deep caves), it is changed into crystal 

 or similar matter, and never resumes its form. 



Let the fifth be that which we term the motion of continuity 

 We do not understand by this simple and primary continuity 

 with any other body (for that is the motion of connection), but 

 the continuity of a particular body in itself ; for it is most 

 certain that all bodies abhor a solution of continuity, some more 

 and some less, but all partially. In hard bodies (such as steel 

 and glass) the resistance to an interruption of continuity is 

 most powerful and efficacious, whilst although in liquids it 

 appears to be faint and languid, yet it is not altogether null, but 

 exists in the lowest degree, and shows itself in many experiments, 

 such as bubbles, the round form of drops, the thin threads which 

 drip from roofs, the cohesion of glutinous substances, and the 

 like. It is most conspicuous, however, if an attempt be made 

 to push this separation to still smaller particles. Thus, in 

 mortars, the pestle produces no effect after a certain degree of 

 contusion, water does not penetrate small fissures, and the air 



