Antecedents of Motion, Heat, and Light. 95 



have cases of it in the arbitrary distributions of temperature 

 prescribed as " initial'' in the theory of the conduction of heat 

 (see* Cambridge Mathematical Journal, Vol. IV., p. 67, 1843) 

 yet we have no indications whatever of natural instances of it ; 

 and in the present state of science we may look for mechanical 

 antecedents to every natural state of matter which we either 

 know or can conceive at any past epoch, however remote. 



It is by tracing backwards the motions which are at pre- 

 sent observed, according to the known laws of motion and 

 heat, with no limit as to time, that the author arrives at the 

 conclusion that the bodies now constituting our solar system 

 have been at infinitely greater distances from one another in 

 space than they are now. He remarked, that the nebular theory, 

 as ordinarily stated, assuming as it does a previously gaseous 

 state of matter, is not only untrue, but the reverse of the 

 truth, according to the views now brought forward ; since these 

 show evaporation — as a necessary consequence of heat gene- 

 rated by collisions and friction, and the general past and pre- 

 sent tendency of matter is seen to be the conglomeration of 

 solids and liquids, accompanied by a gradual increase of the 

 density of gaseous fluid evaporated through space. 



Professor Helmholz, in a most interesting popular lecture 

 on transformations of natural forces, delivered on the 7th of 

 February last at Konigsberg, has estimated that, if the par- 

 ticles at present constituting the Sun's mass have been drawn 

 together by mutual gravitation from a state of infinite diffusion, 

 as assumed in the nebular theory, (not however a gaseous state, 

 as ordinarily supposed, but a state in which the particles ex- 

 ercise no mutual action except that of gravitation,) the whole 

 heat generated must have amounted to about 28,000,000 ther- 

 mal units centigrade per pound of the sun's mass. This esti- 

 mate would not, as the author of the present paper shows, 

 require any change, whether we assume as the immediately 

 antecedent condition of the Sun's matter a state of infinite 

 diffusion or a state of aggregation in solid masses of any di- 



* " Note on some points in the Theory of Heat," a short article in which it 

 was shown how to test the age of a distribution of heat, by applying a certain 

 criterion of convergence to its expression in the infinite series, characteristic of 

 the external circumstances of the body in which it is given. 



