^{page 168 note 1} Quart. Journ. Geo. Soc., iii., p. 186.

^{page 168 note 2} Proc. Geol. Soc., ii., pp. 548, 596.

^{page 169 note 1} Clay contracts on being heated, but this does not affect the theory.

^{page 169 note 2} This table is calculated on the suppositions that the earth is a sphere, with a radius of 3956 miles, and that rocks expand 000005 for 1° Fahr.

^{page 170 note 1} Theorie de la Chaleur, Paris, 1822.

^{page 171 note 1} I need hardly say that these numbers are introduced as an illustration merely, and make no pretension to accuracy.

^{page 173 note 1} See also Darwin “On Volcanic Phenomena in South America.”—Trans. Geol. Soc., 2nd series, p. 601.

^{page 175 note 1} Being the substance of a Lecture delivered on 30th January, 1873, before the Birkenhead Literary and Scientific Society, Claughton Road, Birkenhead.