242 Mh KELLAND, ON THE MOTION OF 



6. In the same manner, denoting by accented letters the quantities 

 corresponding to a, &c. for the motion of a particle of medium B, 

 we obtain 



whence i" = ia^-^{ ^ „T3(^- - ^A'^ + ^c-)] 



which independently of X is equal to 



.A..{ '■F-'--... .FUt^.j "^•-^'^•... .x| 



2 ^ . ,<T. 



Q,..-l " • » n + 3 • b ' a Pn-l — 1 n 



^ '(P + ')' + D"^ ^^' + J"'^ + Z')' 



7. If we were to suppose every part of medium A to be mixed 

 with a portion of medium Ji according to a given law, all that we 

 should require would be the direct integration of these equations, con- 

 sidering M a constant quantity depending on the relative natures of 

 the media : but it will be more analogous to the nature of the question 

 when applied to air or ether, if we suppose a want of uniformity in 

 the mixture. Conceive, for example, that a given mass of medium 

 A, impregnated with medium B, is enclosed by other portions of the 

 same medium not thus impregnated. 



Let f, be the distance between two consecutive particles in the 

 latter mass: then it is easily seen, that the attraction of the mass of 



A, in the mixture, on a particle at its confines is C— 5-; the quantity 



C depending on the mass so impregnated, 



M 

 and that of the mass of ^ is C -=^; 



