﻿Landscape Marble. 243 



Author exhibited a photograph of one of the dykes ascending 

 vertically through the gabbros. Numerous dykes and veins of the 

 same material, not visibly connected with the main granophyre- 

 mass, traverse the gabbros of the ridge of which Druim an Eidhne 

 forms a part. Some of these are described in the paper, and 

 it is shown that the flow-structure follows the irregularities of 

 the gabbro-walls and sweeps round enclosed blocks of altered 

 gabbro. The ' inclusions ' described by Prof. Judd are portions 

 of these dykes and veins. There is not, so far as the Author could 

 discover, a single granite-block enclosed in the gabbro anywhere to 

 be seen at this locality. He therefore claims not only that his 

 original description of the relations of the rocks was perfectly 

 correct, but that the evidence brought forward to contradict it by 

 Prof. Judd furnishes the most crushing testimony in its favour. 



2. 'Note on the Genus Naiadites, as occurring in the Coal 

 Formation of Nova Scotia.' By Sir J.William Dawson, K.C.M.Gr., 

 LL.D., F.R.S., F.G.S. With an Appendix by Dr. Wheelton Hind, 

 B.S., F.R.C.S., P.G.S. 



March 7th. — Dr. Henry Woodward, P.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. ' The Systematic Position of the Trilobites.' By H. M. Bernard, 

 Esq., M.A., F.L.S., F.Z.S. 



2. 'Landscape Marble.' By Beeby Thompson, Esq., F.G.S., 

 F.C.S. 



The Cotham Stone is a hard, close-grained, argillaceous limestone 

 with conchoidal fracture. The dark arborescent markings of the 

 stone rise from a more or less stratified dark base, spread out as 

 they rise, and terminate upwards in wavy banded portions of the 

 limestones. In some specimens two 4 landscapes ' are seen, one 

 above the other, each rising from a distinct dark layer. 



The Author describes the microscopical and chemical characters 

 of the rock, and its mode of occurrence, and discusses the explana- 

 tions which have been put forward to account for its formation, 

 especially that of Edward Owen, who in 1754 gave the first published 

 description of the Cotham Stone, and that advanced by Mr. H. B. 

 Woodward in the ' Geological Magazine ' for 1892. He then pro- 

 poses a new explanation to account for the formation of the rock, 

 and maintains that its peculiar characters are due to interbedded 

 layers of vegetable matter, which decomposed and evolved carbonic- 

 acid gas and marsh-gas. This decomposition continued while several 

 inches of new sediment were laid down, the result being that arbor- 

 escent markings were produced along the lines taken by the escaping 

 bubbles, and that the upward pressure of these gases, after their 

 escape had been prevented by increasing coherence or greater 

 thickness of the upper layers of sediment, caused the corrugations 



