II. DR. BRAUN has earned by his excellent series of observations on sunspots (NATURE, vol. xxxy. p. 227) a title to be heard with particular respect on subjects connected with solar physics. In unfolding his views regarding them in the three concluding sections of his work on Cosmogony, he by no means underrates the difficulties they present. The range of our sensible experience shrinks into absolute insignificance when compared with the exalted conditions reigning in the sun. The temperature at its surface may well reach 40,000° to 100,000° C.; near the centre it mounts probably (our author considers) to ten, possibly to thirty or more million degrees. This unimaginable vehemence of heat is balanced by an unimaginable urgency of pressure. The statement that, in the depths of the sun's interior, it reaches a maximum of 2,000,000,000 atmospheres gives only nominal expression to its value. Figures can at times keep pace with facts only on the condition of being reduced to empty and meaningless symbols.