Abstract

In a paper published in 1901 by the present writer, in collaboration with Dr. C. Lloyd Morgan, an account is given of the igneous rocks of the Tortworth Inlier, the divergent views of previous writers as to the contemporaneous or intrusive character of the rocks are summarized, and the occurrence of fossiliferous calcareous tuffs is proved, leading to the conclusion that the associated ‘trap’-rocks are lava-flows of Silurian age. The exposures of ‘trap’ in the neighbourhood of Woodford and Middlemill are considered to belong to the lower of the two trap-bands.

A second paper by the present writer, in this case in collaboration with Dr. F. R. Cowper Reed, published in 1908, was concerned only with the fossiliferous Silurian rocks. The work, however, led to the conclusion that the trap of Woodford and Middlemill does not belong to the lower band, but is really part of the upper band shifted northwards by a fault (see fig. 3, Q. J. G. S. vol. lxiv, 1908, p. 518). Further information relative to the igneous rocks, obtained when working at the above paper, was published in 1908 in the report of a committee of the British Association, appointed to investigate the pre-Devonian rocks of the Mendips and Bristol area. In this report reason is given for doubting whether the lower trap-band may not, after all, be intrusive. The rocks are exposed:—

• (1) by the stream about 300 yards south-east of Charfield railway-station;

• (2) in two old quarries, one