A SYSTEM OF PARTICLES. 287 



This seems to be connected with the fact of Electro-Magnetism, in 

 which a current produces a force in a plane perpendicular to its direc- 

 tion. I said a force, but it will easily be conceived that if a system 

 be put in motion, and some other body containing similar particles 

 be within its sphere, the effect will be a repulsion in the direction 

 of the motion, as a particle within the body will have a tendency 

 to motion. 



58. The conclusions at which we have arrived, as to the difference 

 of motion in the two systems of fluids, seem also to bear upon this 

 point ; for, from our analysis, it appears that the motion of one fluid 

 will be exactly the opposite of that of the other. The greatest diffi- 

 culty that Electro-Magnetism presents, is the circumstance that each 

 system acts always in one direction. 



It is foreign to my present purpose to consider this point, but 

 it seems probably connected with the circumstance that a flow of 

 Galvanism necessarily commences from the source ; whether that be 

 the positive or negative, I am not prepared to say. 



59. In conclusion I would observe, that nothing which I have 

 advanced has the slightest tendency to invalidate the results to which 

 M. Fourier and others have been led. 



The equations which they obtain may be deduced from the prin- 

 ciples of this method with the same facility as from their own. I 

 regret that it is not in my power to multiply examples by whicii, 

 not only the application of a process can be tried, but even the truth 

 of the principles be tested. The relation between the sign of a small 

 term in the expansion, when the coefficients are determined by obser- 

 vations of the places of the fixed lines in the spectrum, and the 

 permeability of the substance to heat combined with the place of the 

 hottest point in the spectrum, is of a kind that tends to strengthen 

 our convictions in the truth of the principles when satisfactory ; and, 

 to help us to modify those principles when unsatisfactory : on which 

 account, I cannot help expressing my regret that those Philosophers, 

 who have so admirably shewn the intimate connexion between Heat 



