THE problem of the general state of matter at high temperature is so fundamental in stellar physics that I venture to pursue the discussion with Dr. Jeans (NATURE, Feb. 25, p. 278). I would first thank him for his reply to my letter, which, though I differ from it on a number of points, deals fairly with the questions raised. I still believe I was not exaggerating in saying that Jeans's theory requires that the ions (in giant M stars) should be so large that they jam at densities that of air. Jeans wishes to amend this to 80—air. But my figure represents the order of magnitude of the central density of Betelgeuse according to the usual gas model, and he has himself said that the star contracts as a gas until there are substantial deviations from the gas laws in the central regions. To form his liquid core of higher density it would seem that Betelgeuse must have contracted as a gas to its present radius, and then for unexplained reasons thrown out a gaseous envelope filling the present volume. Or starting from his liquid core of density 80 - air, we have to face the problem of balancing on this a gaseous atmosphere containing much less mass and subject initially to 8000 times the gravitation of the ordinary model. I think that to achieve this Dr. Jeans will have to depart much more widely from current theory than he intended.