NOVUM ORGANUM 259 



Let the twelfth motion be that of excitement, which 

 appears to be a species of the last, and is sometimes men 

 tioned by us under that name. It is, like that, a diffu 

 sive, communicative, transitive and multiplying motion; 

 and they agree remarkably in their effect, although they 

 differ in their mode of action, and in their subject matter. 

 The former proceeds imperiously and with authority; it 

 orders and compels the assimilated to be converted and 

 changed into the assimilating body. The latter proceeds 

 by art, insinuation and stealth, inviting and disposing the 

 excited toward the nature of the exciting body. The for 

 mer both multiplies and transforms bodies and substances; 

 thus a greater quantity of flame, air, spirit and flesh is 

 formed; but in the latter, the powers only are multiplied 

 and changed, and heat, the magnetic power, and putrefac 

 tion, in the above instances, are increased. Heat does not 

 diffuse itself when heating other bodies by any communica 

 tion of the original heat, but only by exciting the parts of 

 the heated body to that motion which is the form of heat, 

 and of which we spoke in the first vintage of the nature 

 of heat. Heat, therefore, is excited much less rapidly and 

 readily in stone or metal than in air, on account of the in 

 aptitude and sluggishness of those bodies in acquiring that 

 motion, so that it is probable, that there may be some sub 

 stances, toward the centre of the earth, quite incapable of 

 being heated, on account of their density, which may de 

 prive them of the spirit by which the motion of excitement 

 is usually commenced. Thus also the magnet creates in the 

 iron a new disposition of its parts, and a conformable mo 

 tion, without losing any of its virtue. So the leaven of 

 bread, yeast, rennet and some poisons, excite and invite 

 successive and continued motion in dough, beer, cheese or 



