In the very interesting paper by Mr. Arthur Holmes on “Rradio-activity and the Earth's Thermal History”, in the Geological Magazine for February and March, it is assumed that in Archæan times there was “a widespread molten condition at no very great depth” below the earth's surface, and in the final conclusions the statement is made that “geological and other evidence points favourably to the traditional view that the earth's crust was initially in a molten state”. The results of recent work on the Archæan of Canada do not bear out this traditional view of the conditions of the earth's earliest known geological period, and it may not be amiss to suggest some points that decidedly conflict with it.