Note 249 — Chapter XIII · THE ERUPTIONS OF LLANDEILO AND BALA AGE
Reading edition
See Mr. F. Rutley, "The Felsitic Lavas of England and Wales," Mem. Geol. Surv. 1885, pp. 12-15; also the description of Messrs. Harker and Marr, Quart. Journ. Geol. Soc. xlvii. (1891), p. 301.
[250] Unfortunately these acid lavas are not distinguished from the others in the Geological Survey maps.