378 NOVUM ORGANUM. 



other, and sometimes are collected and attracted together from some 

 distance ; as when in milk, after standing some time, the cream rises 

 and swims on the top ; while in wine the dregs and tartar fall to the 

 bottom. Nor is this owing to the Motion of Heaviness and Lightness 

 alone, causing some particles to rise to the top, and others to sink to 

 the bottom ; but in a much greater degree to the desire felt by homo 

 geneous bodies to combine and unite among themselves. And this 

 motion differs from the Motion of Want in two particulars. One is 

 that in the Motion of Want there is at work the stronger stimulus of 

 a malignant and contrary Nature ; whereas in this motion (provided 

 there be nothing to hinder or coerce it) the particles unite from friend 

 ship, although there be no foreign Nature present to stir up strife. 

 The other is, that the union here is closer, and in it greater choice is 

 exercised. In the former, only let the hostile body be avoided, and 

 bodies which are not very much akin will come together ; while in 

 the latter, substances meet because they are connected by a distinct 

 relationship, and are drawn together, as it were, into one. And this 

 motion exists in all composite bodies, and would readily show itself 

 in each of them, were it not tied and bound by other appetites and 

 necessities in the bodies, which interfere with that union. 



Now restraint is put upon this motion in three ways : by the torpor of 

 bodies ; by the check of a discordant body ; and by external motion. 

 With regard to the torpor of bodies, it is certain that there is in 

 tangible bodies a certain sluggishness, more or less, and a dislike to 

 motion in space ; so that, unless they be excited, they prefer remain 

 ing in their present condition to changing for the better. Now this 

 torpor is shaken off by the help of three things : either by heat, or by 

 the eminent virtue of some cognate body, or by a lively and powerful 

 motion. And, as regards the aid of heat, it is for this reason that 

 heat is designed to be that which separates what is heterogeneous ana 

 combines what is homogeneous ; a definition of the Peripatetics which 

 has been deservedly ridiculed by Gilbert, who says that it is much the 

 same as if a man were to be defined as that which sows wheat, and 

 plants vines for that it is a definition by means of effects alone, and 

 those particular ones. But the definition has something worse about 

 it, since those effects (such as they are) are owing not to the peculiar 

 properties of heat, but only to accident (for cold does the same, as we 

 shall show hereafter), namely, to the desire of the homogeneous parts 

 to unite ; heat helping only so far as to dispel the torpor which had 

 previously fettered the desire. And as for help rendered by the virtue 

 of a cognate body, it is marvellously well shown in the armed magnet, 

 which excites in iron the virtue of detaining iron, by similarity of 

 substance, the torpor of the iron being dispelled by the virtue of the 

 magnet. And with reference to help rendered by motion, it is con 

 spicuous in wooden arrows, which have also points of wood, for these 

 penetrate deeper into wood than if they were tipped with iron, owing 

 to the similarity of substance, the torpor of the wood being dispelled 

 by the rapid motion ; and of these two experiments we have spoken 

 also in the Aphorism on Clandestine Instances. 



