NOVUKf ORGANUM. 383 



body respectively ; not so much by the force of the exciting, as from 

 the predisposition and easy yielding of the excited body. 



13. Let the thirteenth Motion be the Motion of Impression, which 

 is also of the same genus with the Motion of Assimilation, and is 

 the most subtle of all diffusive motions. But we have thought fit to 

 constitute it into a species by itself, on account of the remarkable 

 difference between it and the two former. For the simple Motion of 

 Assimilation transforms the bodies themselves ; so that if you take 

 away the first moving agent, there will be no difference in what 

 follows. For the first kindling into flame, or the first turning into air, 

 has no effect on the flame or air of the next generation. In like 

 manner the Motion of Excitation remains when the first mover is 

 removed for a considerable length of time, as in a heated body when 

 the first heat has been removed ; in excited iron when the magnet 

 is removed ; in dough when the leaven is removed. But the 

 Motion of Impression, although it is diffusive and transitive, yet 

 seems ever to depend on the prime mover, so as, on its removal 

 or cessation, immediately to fail and perish ; and therefore the 

 result is arrived at in a moment, or, at least, in a short space of 

 time. Wherefore we usually call the Motions of Assimilation and 

 Excitation, Motion of the Generation of Jupiter, because the genera 

 tion remains ; and the latter motion we call the Motion of the Gene 

 ration of Saturn, because the birth is immediately devoured and 

 absorbed. This motion manifests itself in three ways : in the rays 

 of light ; in the percussion of sounds ; and in magnetic action, as far 

 as communication is concerned. For, if light be removed, colours 

 and its other images immediately vanish ; if the first percussion and 

 the consequent agitation of the body be done away with, the sound 

 soon after dies away. For though sounds are disturbed during their 

 course by winds, as if by waves, yet we must be careful to remark that 

 the sound docs not last all the time that the resonance is going on. 

 For when a bell is struck the sound seems to continue for a con 

 siderable time, whence one might easily fall into the error of thinking 

 that during the whole of that time the sound is, as it were, floating 

 and hanging in the air, which is most untrue. For the resonance is 

 not numerically the same sound, but a renewal of it ; and this is 

 shown clearly by quieting or restraining the percussion of the body. 

 For if the bell be held tight, so that it cannot move, the sound imme 

 diately dies away, and resounds no longer; as in stringed instruments, 

 if after the first percussion the string be touched with the finger, as in 

 the lyre ; or with a reed, as in the spinet ; the resonance immediately 

 ceases. And when the magnet is removed the iron straightway falls. 

 The moon cannot be removed from the sea, nor the earth from a 

 falling body possessed of weight : and therefore we cannot make any 

 experiments concerning them ; but the principle is the same. 



14. I^et the fourteenth Motion be the Motion of Configuration, or 

 Position, by which bodies seem to desire not combination, or separa 

 tion of any kind, but position, collocation, and configuration, with 

 respect to others. And this motion is a very abstruse one, and has 



