The Earth's Thermal History

Abstract

DR. J. H. J. POOLE has kindly pointed out to me that the reference to the adiabatic gradient of temperature in my previous letter¹ is capable of being understood to mean that he believes that the adiabatic gradient in a liquid heated below would not be maintained. This was not intended; the maintenance of the adiabatic gradient by convection currents (or rather, of one exceeding it by the trifling amount needed to start and maintain convection currents) is essential both to his views and mine. My point was simply that excess heat would be carried up by convection currents, as in the formation of cumulus clouds on a summer day, while a passage in his letter had appeared to cast doubt on this.