274 Mr KELLAND, ON THE MOTION OF 



-4{'- 



2r' 2. 4 r 2 r ' 



Suppose the particle under consideration situated at the confines of 

 a medium, whose temperature is less than that of the medium in 

 wliicli the uniform motion has been transmitted; we have then a = 0, 

 and the force exerted 



= j1 .(b^ + C-) suppose, 



omitting the variable part, so that the value of a in this instance 

 depends on b^ + cr. 



It will readily be perceived that the above investigation has refer- 

 ence to the possibility of a transmission of the particles whilst they 

 are in a state of vibration. And since we have shewn that the ten- 

 dency to motion forwards varies as the extent of the vibratory motion, 

 we have stumbled upon an interpretation which coincides with the 

 physical characters of Heat. 



42. But all that we have hitherto done is to suppose the motion 

 of a series of particles, symmetrically situated with respect to the 

 axes. Such an investigation will probably be correct for Light, but 

 when treating of the transmission of Heat, the contrary must un- 

 doubtedly be adopted. 



Leaving out of the question then the above investigation which 

 may apply to constant radiation, and which is nearly identical with 

 I^eslie's hypothesis, we come to the case of a medium having more 

 particles on one side of a plane, parallel to that of y&, than on the 

 other; and our object is to determine the initial velocity and motion 

 of transmission of a particle along the axis of .v. 



We shall in this investigation suppose no reciprocating motion of 

 the particles along the axis, and consider them to have had no velocity 

 of transmission, which supposition will not affect the results due to 



