334 Remarks on Prof. Potter's Theorij of Sound. 



adjoining cubes where they are in contact, and as we assumed the 

 pressure on the unit of left face to be due to the attributed cube 

 {ot/S)^, we must now assume the left face to have a smface repre- 

 sented by («,S)^ ; and similarly, the right face of the cube ^ will 

 be pressed by the cube 7, through an extent represented by (^7)^. 

 This is the only supposition I can conceive which will save Prof. 

 Potter's theory from theinconsistcncy of first assuming the cubes 

 a, /8, 7 to be unequal, and then tacitly assuming their equality. 

 Introducing the above values for the left and right faces of the 

 cube {/3) pressed on by the cubes (a) and (7), we find the equa- 

 tion of motion becomes 



df \{oc^) {l3y)J' • • • • ^ 



which, on introducing the values of (a/3) and {I3y) above found 

 becomes ^2,. 



dF~ fd^^ ^ ^^ 



\dx) 

 This is the old equation of propagation of sound, from which 



3 



the coefficient ^ has entirely disappeared. 



From the foregoing investigation, we are entitled to conclude 

 that Professor Potter's theory does not lead to the equation 



d'^ij _ 3k dx 

 ~dP ■" 



3 /rfyy 

 \dx) 



(4.) 



Although the theory which has been above discussed leads to 

 equation (3.) as M'ell as the common theoiy, yet it appears open 

 to the following objections : — 



1 . The cubical form of atoms assumed by this theory of gases 

 is very unnatural, and by no means sanctioned by the chemical 

 doctrine of atoms, which does not suppose the expansion or con- 

 traction of individual atoms. 



2. It would follow from this cubical arrangement, that motion 

 in a gas would be pro])agated according to the known law only 

 in three directions perpendicular to the faces of the cubes. — 

 N.B. If this be denied, then the atoms are not cubes but spheres. 



3. X disturbance of density in a gas would produce interstices 

 throughout the mass, which are inconceivable. — N.B. If this be 

 denied, then the atoms have changed their form, and are no 

 longer cubes. 



Trinitv College, Dublin, 

 Mai-ch 22, 1851. 



