Vol. 50.] MR. B. THOMPSON ON LANDSCAPE MARBLE. 393 



25. Landscape Marble. By Beeby Thompson, Esq., F.G.S., F.C.S. 

 (Read March 7th, 1894.) 



Contents. 



Page 



I. General Description of the Landscape Marble 393 



II. Specific Description of the Landscape Marble 394 



III. Its Microscopic Characters 396 



IV. Its Chemical Characters 398 



V. Its Mode of Occurrence 399 



VI. Theories as to the Origin of the Landscape Marble 399 



VII. Mode of Formation of the Landscape Marble 401 



VIII. Experiments made to reproduce the Characteristics of Landscape 



Marble 405 



IX. Conditions under which the Landscape Marble was formed 406 



I was led to a study of the structure and origin of the so-called 

 Landscape Marble, or Cotham Stone, through reading an article in 

 the Geological Magazine for 1892, p. 110, by Mr. H. B. Woodward, 

 entitled, ' Remarks on the Formation of Landscape Marble.' To 

 that article I am much indebted for information as to the general 

 characteristics of the stone, and its mode of occurrence. 



The first published description of the Landscape Marble occurs 

 in a work by Edward Owen, the title of which is ' Observations on 

 the Earths, Rocks, Stones and Minerals, for some miles about 

 Bristol, and on the Nature of the Hot Well and the Virtues of its 

 Water ' ; the date on the title-page being 1754. The name 'Gotham 

 Stone ' was applied to the Landscape Marble because it was 

 quarried, with other material, near Cotham House, on the northern 

 side of Bristol, but Owen did not give it this name ; he merely 

 adopted the appellation by which it was already known in that part 

 of the country (op. cit. p. 164). 



At the time of Owen the Cotham Stone was chiefly known by 

 and valued for its peculiar, corrugated, upper surface, ' rustick ' 

 so-called, though some cut and polished specimens were to be found 

 framed in the houses of ' the gentlemen of the neighbourhood.' 



For convenience of reference, I shall number the descriptive 

 paragraphs throughout this paper. 



I. General Description of the Landscape Marble. 



1. It is a hard, close-grained, argillaceous limestone, which breaks 

 with a fracture almost as conchoidal as flint ; and it takes a 

 moderate polish. 



2. It shows no distinct evidence of concretionary origin, although 

 concentric layers will sometimes flake off the upper surface. 



3. The ujyper surface is often much wrinkled, and the irregularities 

 appear to correspond with the original planes of deposition, for 

 when a layer flakes off it follows these irregularities. The wrinklings 



