430 Rev. J, B. Emmet t on the [June, 



since the particles will soon come into contact, and of course 

 preserve a state of rest. And if more of these systems be added, 

 and systems themselves be made to oscillate, a state of rest will 

 be attained very speedily and sooner in a large mass than in a 

 smaller ; but a large body retains its heat longer than a smaller 

 one oi* the same kind of matter. The only motion that can be 

 permanent is one of revo- 

 lution. Let two particles 

 A and B, equal and simi- 

 lar, revolve in a non-resist- 

 ing medium ; their revolu- 

 tion round S the common 

 centre of gravity, and the 

 centre of their common 

 orbit may be continued indefinitely. Add another system, equal 

 and similar, revolving round their common centre of gravity s; 

 join S s, and bisect it in T. The motion of each system might 

 continue independently of the other; but each particle of one 

 being attracted by each of the other, the two equal systems must 

 approach each other in the direction S s, and soon destroy each 

 other's motion, except they revolve round T their common centre 

 of gravity : add more systems, and they must all revolve round 

 the common centre of gravity of the whole. If, therefore, any 

 body be not at the absolute zero of temperature, there must be a 

 motion of the whole of its parts round its centre of gravity, which 

 in solids is impossible, and in liquids and gases would be evident 

 by vortices which of necessity must produce mechanical effects, 

 which is not the case. Besides this, the motion could only exist 

 in a non-resisting medium ; under the pressure of the air, and 

 the weight of the body, it must be instantly destroyed. A solid 

 could not retain its heat for many hours, since all must attain a 

 state of rest in nearly the same time. This motion is also phy- 

 sically impossible, if the force of attraction be supposed to vary 

 inversely as the cube of the distance ; for if a body revolve round 

 a centre of force, and be so attracted, its orbit must be a circle, 

 or a logarithmic spiral, the former only being permanent, and 

 revolving in a circle, if it be disturbed by any other force, which 

 it must be by the attraction of adjacent particles, the weight of 

 the mass, and pressure of the air, it becomes a logarithmic spiral 

 approaching to the pole ; and attaining this, all motion ceases ; 

 and when this is the case, the body becomes absolutely cold. 

 In addition, whatever be the force of attraction, since cohesion 

 vanishes when the particles of a body are separated to the least 

 possible distance from contact, it is absolutely impossible for 

 there to be any cohesion in solids if the particles have any such 

 motion, since they never can touch each other. A motion of 

 this sort, therefore, cannot continue ; and it will cease in nearly 

 the same space of time in all masses of the same matter. The 

 motion itself may be now proved to be impossible, and, if it did 



