118 Mr. W. Ramsay on the Critical 
mum or minimum values in the interior of the fluid ; but then 
the angular velocity O cannot have there a maximum value, 
which, taking the axis of x parallel to the direction of the 
rotation-axis, would correspond obviously with a maximum 
value of £. 
2nd. That though the idea of the possible existence of 
unstable solutions of the equations of motion (alluded to, as 
far as I know, for the first time by Prof. Stokes*) was very 
just and fertile in itself, yet the case of motion which sug- 
gested it to him is not one of unstable motion, at least not so 
unless the squares and products of velocities be taken into 
account. It is perfectly true that, when a cylinder of infinite 
length moves with uniform velocity through an incompressible 
viscous fluid, the state of steady motion never can be reached, 
and an ever increasing quantity of fluid will be carried on by 
the cylinder. Yet as the dissipation of energy will be ever 
decreasing, and even, as may be proved, tending to zero, as 
the motion proceeds, such a change in the state of motion as 
Prof. Stokes alludes to, and by which the dissipation of energy 
could o ily be augmented, cannot occur. 
When, on the contrary, the squares and higher powers of 
the velocities are taken into account, I have my reasons for 
supposing that, even in the case of a sphere moving with uni- 
form velocity, no state of steady motion can be reached, and 
the motion must finally become unstable. 
Amsterdam, June 4, 1883. 
XVIII. On the Critical Point of Liquefia de Gases. 
By William Ramsay. 
To the Editors of the Philosophical Magazine and. Journal. 
Gentlemen, 
IN the July number of this Magazine there is a translation 
of a memoir by 1\L. J. Jamin, presented bv him to the 
French Academy. As he has taken no notice of the views 
expressed by me in the 'Proceedings of the Royal Society" for 
1880, April 22nd and December 16th, I think it right to point 
out that the substance of this memoir has been anticipated ; 
and in support of this statement let me quote the following 
pas-ages. M. Jamin states (1) that the critical point of a 
liquid is not to be regarded, as hitherto, as the temperature at 
* Trans, of the Camb. Phil. Soc. vol. ix. 1849, « On the Effect of the 
Internal Friction of Fluids on the Motion of Pendulums," p. 5G. 
