NOVUM ORGAN UM. 185 



tartar sink ; which effects are not to be attributed to gravity 

 and levity only, so as to account for the rising of some parts 

 and the sinking of others, but much more, to the desire of 

 the homogeneous bodies to meet and unite. This motion 

 differs from that of need in two points: 1st, because the 

 latter is the stimulus of a malignant and contrary nature ; 

 whilst in this of which we treat (if there be no impediment 

 or restraint), the parts are united by their affinity, although 

 there be no foreign nature to create a struggle ; 2dly, be 

 cause the union is closer and more select. For, in the 

 other motion, bodies which have no great affinity unite, if 

 they can but avoid the hostile body, whilst in this, sub 

 stances which are connected by a decided kindred resem 

 blance come together and are moulded into one. It is a 

 motion existing in all compound bodies, and would be 

 readily seen in each, if it were not confined and checked 

 by the other affections and necessities of bodies which dis 

 turb the union. 



This motion is usually confined in the three following 

 manners : by the torpor of the bodies ; by the power of the 

 predominating body ; by external motion. With regard to 

 the first, it is certain that there is more or less sluggishness 

 in tangible bodies, and an abhorrence of locomotion : so 

 that unless excited they prefer remaining contented with 

 their actual state, to placing themselves in a better position. 

 There are three means of breaking through this sluggish 

 ness ; heat ; the active power of a similar body ; vivid and 

 powerful motion. With regard to the first, heat is, on this 

 account, defined as that which separates heterogeneous and 

 draws together homogeneous substances; a definition of 

 the Peripatetics, which is justly ridiculed by Gilbert, who 

 says it is as if one were to define man, to be that which 

 sows wheat and plants vineyards ; being only a definition 

 deduced from effects, and those but partial. But it is still 

 more to be blamed, because those effects, such as they are, 

 are not a peculiar property of heat, but a mere accident 

 (for cold, as we shall afterwards show, does the same), 

 arising from the desire of the homogeneous parts to unite ; 

 the heat then assists them in breaking through that slug 

 gishness, which before restrained their desire. With regard 

 to the assistance derived from the power of a similar body, 

 it is most conspicuous in the magnet when armed with 

 steel, for it excites in the steel a power of adhering to steel, 

 as a homogeneous substance, the power of the magnet 

 breaking through the sluggishness of the steel. With 



