538 KOVUM ORGANUM. [BOOK 11. 



tlicrofore, must be determined by experiment, and not by pro- 

 bability or conjecture. 



Lastly, we must in all our inrestigations of nature obserre 

 wbat quantity, or dose, of the body is requisite for a given effect, 

 and must at the same time be guarded against estimating it at 

 too much or too little. 



XLVIII. In the twenty-fourth rank of prerogative instances 

 we will place wrestling instances, which we are also wont to call 

 instances of predominance.- They are such as point out tho 

 predominance and submission of powers compared with each 

 other, and which of them is the more energetic and superior, or 

 more weak and inferior. For the motions and effects of bodies 

 are compounded, decomposed, and combined, no less than the 

 bodies themselves. We will exhibit, therefore, the principal 

 kinds of motions or active powers, in order that their comparative 

 strength, and thence a demonstration and definition of the 

 instances in question, may be rendered more clear. 



Let the first motion be that of the resistance of matter, which 

 exists in every particle, and completely prevents its annihilation ; 

 80 that no conflagration, weight, pressure, violence, or length of 

 time can reduce even the smallest portion of matter to nothing, 

 or prevent it from being something, and occupying some space, 

 and delivering itself (whatever straits it be put to), by changing 

 its form or place, or, if that be impossible, remaining as it is ; nor 

 can it ever happen that it should either be nothing or nowhere. 

 This motion is designated by the schools (which generally name 

 and define everything by its effects and inconveniences rather 

 than by its inherent cause) by the axiom, that two bodies can- 

 not exist in the same place, or they call it a motion to prevent 

 the penetration of dimensions. It is useless to give examples of 

 this motion, since it exists in every body. 



Let the second motion bo that which we term the motion of 

 connection, by which bodies do not allow themselves to be sepa- 

 rated at any point from the contact of another body, delighting, 

 as it were, in the mutual connection and contact. This is called 

 by the schools a motion to prevent a vacuum. It takes place 

 when water is drawn up by suction or a syringe, the flesh by 

 cupping, or when the water remains without esca])ing from per- 

 forated jars, unless the mouth be opened to admit the air, and 

 innumerable instances of a like nature. 



Let the third be that which we term the motion of liberty, by 

 which bodies strive to deliver themselves from any unnatural 

 pressure or tension, and to restore themselves to the dimensions 

 suited to their mass ; and of which, also, there are innumerable 

 examples. Thus, we have examples of their escaping from pres- 

 gure, in the water in swimming, in the air in flying, in the water 

 again in rowing, and in the air in the imdulation of the winds, 



