[402] Playfair's Illustrations of the Huttonian Theory, § 255 et seq.
[403] Trans. Roy. Soc. Edin. (1805), vol. v. p. 43.
[404] Mem. Wern. Soc. ii. 178, 618; iii. 25; Edin. Phil. Journ. i. 138, 352; xv. 386.
[405] Trans. Roy. Soc. Edin. (1811), vi. p. 405.
[406] Tracts and Observations in Natural History and Physiology, 8vo, Lond. 1799.
[407] Trans. Roy. Soc. Edin. (1833), xiii. pp. 39, 107.
[408] Essai géologique sur l'Écosse. Paris; no date, probably 1820.
The first broad general sketch of the Carboniferous igneous rocks of a large district of the country was that given by Hay Cunningham in his valuable essay on the geology of the Lothians.[409] He separated them into two series, the Felspathic, including "porphyry" and "clinkstone," and the Augitic or Trap rocks. To these he added "Trap-tufa," which he considered to be identical in origin with modern volcanic tuff. It was the eruptive character of the igneous rocks on which he specially dwelt, showing by numerous sections the effects which the protrusion of the molten masses have had upon the surrounding rocks. He did not attempt to separate the intrusive from the interstratified sheets, nor to form a chronological arrangement of the whole.
[409] Mem. Wern. Soc. vii. p. 1. Published separately, 1838.
Still more important was the sketch given by Maclaren, in his classic Geology of Fife and the Lothians.[410] This author clearly recognized that many of the igneous rocks were thrown out contemporaneously with the strata among which they now lie. He constantly sought for analogies among modern volcanic phenomena, and presented the Carboniferous igneous rocks of the Lothians not as so many petrographical varieties, but as monuments of different phases of volcanic action previous to the formation of the Coal-measures. His detailed descriptions of Arthur Seat and the rocks immediately around Edinburgh, which alone the work was originally intended to embrace, may be cited as models of exact and luminous research. The portions referring to the rest of the basin of the Forth did not profess to be more than a mere sketch of the subject.