(19) On the other hand, if the pressure of the gas is ke p t constant throughout the motion, T/v is constant and dQ = **JC**,,NmdT, whence C 5 = z (n +5) R /Jm.

Hence these displacements are proportional to, JD, **JC**, and A therefore to DD, CC, where ~ CD is any line drawn FIG.

(usually a~ small circle of the fixed sphere), and join JA, JB, **JC**, AB, BC

If these lines be turned through a right angle in the same sense, they take up positions such as CC, DID, where C, D are on **JC**, JD, respectively, and CD is parallel to CD.