Note 4 — Chapter III · ISLAND OF MULL AND ADJOINING COAST.
Reading edition
History of Volcanic Action, etc., loc. cit. p. 153, et seq. The "Granophyres" of Geikie come under the head of "Felsites," passing into "granite" in one direction and quartz-trachyte in another, according to Judd; the proportion of silica from 69 to 75 per cent.—Quart. Jour. Geol. Soc., vol. xxx. p. 235.