OF MOLECULAR VORTICES. 563 



state, the coefficient given in equation (9) is the specific heat at constant volume; 

 and as that quantity is known to be constant at all temperatures, the second 

 term of the right hand side of the equation disappears, and it is reduced simply 

 to the following — 



Jc -2 Po t • • • W 



The specific heat, in dynamical units per degree, of a perfect gas under 

 constant pressure, is expressed as follows : — 



3c' = 3c + &- = 2*- (? + l) • • • . (13); 



and the ratio in which the latter coefficient is greater than the former is, 

 therefore, 



h 1 + l < 14 >; 



whence we have the following formulae for deducing the proportion k, borne by 

 the total energy of the thermal motions to the energy of the steady circulation, 



from the ratio — as determined by experiment, 



* = 37PT> (15) ' 



This method is applicable only to substances that are nearly in the perfectly 

 gaseous state. 



There is another method, applicable to the same class of substances, which is 

 expressed as follows : — 



k= 2 -?f^ (16). 



3p 



This second method may be applied to liquids and solids also, under the follow- 

 ing conditions ; the quantity -^ is to be calculated as for the perfectly gaseous 



state; and the specific heat c must be nearly constant. 



The ratio which the energy of periodical disturbances in an unit of volume 

 bears to the centrifugal pressure may be interesting in connection with hypo- 

 thetical views of the constitution of matter. It is expressed as follows : — 



fci> (17). 



