46 LETTEE TO PROFESSOR NERNST conclusions. But I have a difficulty in accepting it as a picture c actually takes place. We do well, I think, to concentrate attention upon the diatomic molecule. Under the influence of collisions the molecule freely and acquires rotation. Why does it not also acquire vibration along t joining the two atoms ? If I rightly understand, the answer of PL that in consideration of the stiffness of the union the amount of ener. should be acquired at each collision falls below the minimum possil that therefore none at all is acquired—an argument which certainly paradoxical. On the other hand Boltzrnann and Jeans contend that i a question of time and that the vibrations necessary for full statistic; librium may be obtained only after thousands of years. The calculai Jeans appear to show that there is nothing forced in such a view. I like to inquire is there any definite experimental evidence against it ? as I know, ordinary laboratory experience affords nothing decisive. I am yours truly, RAYLEIG:ing an elastic body to be rather stiff, the vibrations have their full share and this share cannot be diminished by increasing the stiffness. For this purpose the simplification fails, which is as much as to say that the method of generalized coordinates cannot be applied. The argument becomes, in fact, self-contradictory.