Note 339 — Chapter XVII
Reading edition
Two analyses of rhyolites from Shetland by Mr. Tatlock will be found in Trans. Roy. Soc. Edin. vol. xxxii. (1887), p. 387. Their silica percentage is 72·32 and 73·70. An analysis of a quartz-felsite from the Cheviot Hills by Mr. T. Waller is given in the Geological Survey Memoir on the Cheviot Hills, p. 25. The proportion of silica in this rock is 67·9.