Note 148 — Chapter XXXIII
Reading edition
Report on the Geology of Londonderry, p. 93. There can be no doubt that this was an error of observation. The Antrim basalts are all certainly younger than the Chalk. The supposed "lumps of basalt" were probably the ends of veins intruded into the Chalk, and perhaps partially disconnected from the main parts of the veins. Such apparently detached masses of intrusive rock are not infrequent occurrence in connection with the Tertiary intrusive sills. An example will be found represented in Fig. 321.
[149] Brit. Assoc. Report, 1850, Sections, p. 70; and Quart. Jour. Geol. Soc. vii. (1851), p. 87.