226 Remarks upon Mr. Herapath's Theory. [Sept. 



point. Mr. H. has not proved that any such point exists ; and 

 till that is done, it is premature to think of finding an expression 

 to represent it. 



Mr. H. also endeavours to explain those phenomena which 

 are usually ascribed to latent heat ; a theory which if any theory 

 was ever established by the most direct and decisive experiments, 

 and by the most clear and forcible reasoning, must be eminently 

 considered so ; yet he rejects it, and attempts to explain the 

 phenomena on his own principles : his reasoning, however, 

 appears to me inconclusive. 



His principal step is, that two particles in motion uniting, the 

 motion of this new particle must be compounded of the motions 

 of the others which compose it ; and, therefore, will be greater 

 than the motion of either of the constituent parts before aggre- 



gation. 



But it does not follow that two particles, each moving with a 

 certain velocity, should, when they unite, necessarily move with 

 a greater velocity. If they were moving in opposite directions, 

 and were suddenly united, their motion would cease altogether. 

 If they were moving in directions inclined towards each other 

 at any angle, they would each lose a part of their motion, and 

 the resulting motion would be that arising from the composition 

 of the remaining motions of each. But this is taking for granted 

 that they unite in such a manner as will not affect their motions 

 by the act of union. This, however, cannot be admitted. 



An union cannot take place without some force acting upon 

 one or both of the particles. Thus each particle would be urged 

 by two motions ; that with which it was before moving, and that 

 with which it approaches the other particle ; and, therefore, its 

 motion in the former direction must be diminished. 



It is also what, I think, Newton would call u durior hypothe- 

 sis," to conceive that the particles of a solid should move among 

 themselves with greater velocity than those of a fluid. 



Thus I have, 1 hope without offence, stated a few objections 

 and difficulties which have occurred to me in reading Mr. Hera- 

 path's papers. Should these remarks be thought worth atten- 

 tion, I may, perhaps, trouble you with a few more on the other 

 parts of his inquiries; and with such remarks, if communicated 

 with candour, Mr. H. himself cannot be displeased, as he has 

 professed it his wish to excite inquiry and examination into the 

 validity of his system. I am, &c. X. 



