6 NATURAL HISTORY. 



shivers and fitters ; the motion, upon the pressure, 

 searching all ways, and breaking where it findeth 

 the body weakest. 



11. The powder in shot, being dilated into such 

 a flame as endureth not compression, moveth like 

 wise in round, the flame being in the nature of a 

 liquid body, sometimes recoiling, sometimes breaking 

 the piece, but generally discharging the bullet, be 

 cause there it findeth easiest deliverance. 



12. This motion upon pressure, and the reci 

 procal thereof, which is motion upon tensure, we use 

 to call, by one common name, motion of liberty ; 

 which is, when any body, being forced to a preter 

 natural extent or dimension, delivereth and restoreth 

 itself to the natural: as when a blown bladder 

 pressed, riseth again ; or when leather or cloth ten- 

 tured, spring back. These two motions, of which 

 there be infinite instances, we shall handle in due 

 place. 



13. This motion upon pressure is excellently also 

 demonstrated in sounds ; as when one chimeth upon 

 a bell, it soundeth ; but as soon as he layeth his hand 

 upon it, the sound ceaseth : and so the sound of a 

 virginal string, as soon as the quill of the jack falleth 

 from it, stoppeth. For these sounds are produced 

 by the subtile percussion of the minute parts of the 

 bell, or string, upon the air ; all one, as the water is 

 caused to leap by the subtile percussion of the mi 

 nute parts of the glass, upon the water, whereof we 

 spake a little before in the ninth experiment. For 



