366 THE CONSERVATION OF FOECE. 



of thought grows up in the mind, if we consider the mutual 

 gravitating action of one particle and many. The particle A 

 will attract the particle B at the distance of a mile with a 

 certain degree of force ; it will attract a particle C at the 

 same distance of a mile with a power equal to that by which 

 it attracts B ; if myriads of like particles be placed at the 

 given distance of a mile, A will attract each with equal force ; 

 and if other particles be accumulated round it, within and 

 without the sphere of two miles diameter, it will attract them 

 all with a force varying inversely with the square of the dis- 

 tance. How are we to conceive of this force growing up in 

 A to a million-fold or more, and if the surrounding particles 

 be then removed, of its diminution in an equal degree ? Or, 

 how are we to look upon the power raised up in all these 

 outer particles by the action of A on them, or by their action 

 one on another, without admitting, according to the limited 

 definition of gravitation, the facile generation and annihilation 

 of force? 



The assumption which we make for the time with regard 

 to the nature of a power (as gravity, heat, etc.), and the 

 form of words in which we express it, that is, its definition, 

 should be consistent with the fundamental principles of force 

 generally. The conservation of force is a fundamental prin- 

 ciple ; hence the assumption with regard to a particular form 

 of force ought to imply what becomes of the force when its 

 action is increased or diminished, or its direction changed ; or 

 else the assumption should admit that it is deficient on that 

 point, being only half competent to represent th$ force ; and, 

 in any case, should not be opposed to the principle of conser- 

 vation. The usual definition of gravity as an attractive force 

 between the particles of matter VABYING inversely as the square 

 of the distance, whilst it stands as a full definition of the 

 power, is inconsistent with the principle of the conservation 

 of force. If we accept the principle, such a definition must 

 be an imperfect account of the whole of the force, and is 



