396 ME. B. THOMPSON ON LANDSCAPE MAEBLE. [Aug. 1 894, 



tudinally striated with thin, darker brown marks. This is rather 

 less than \ inch thick. 



The next portion above (B) is about | inch thick, of a grey colour 

 mostly, and is longitudinally striated with darker, almost black 

 marks. 



The striae in A and B vary in distinctness and distance from each 

 other, but average about 20 to the inch. 



8. The middle portion of the stone is that part where the character- 

 istic arborescent markings occur, which it is the special object of 

 this communication to explain. 



At the base is a dark layer (C) conforming in general curvature 

 with the layers below, but extremely irregular in structure, the 

 upper part being very jagged {the hedge). 



Above the last, but springing from it, are the more decided 

 arborescent markings (D), which may rise in the form of a single 

 stem and then spread out (trees) or may spread out at once (shrubs). 



Between the arborescent parts there is a light-coloured matrix 

 (E), striated, but in a very erratic manner, so that the imaginative 

 eye may see clouds, mountains, lakes, etc. Amidst all the confusion 

 here, however, there is uniformity in one thing, and this is most 

 important : the striae of the matrix are always directed upwards near 

 the dark markings, and dip downwards between them. 



This part of the stone may be taken as 1| inch in thickness. 



9. The upper portion of the stone greatly resembles the lower in 

 change of colour towards the outside, and in being striated, but the 

 uniformity of curvature has evidently been interfered with from 

 below and from above, for the striae rise over the arborescent 

 markings and sink between them, and this is almost exactly what 

 the outside of the stone does. 



Just above the termination of the arborescent markings is a 

 layer, F, which is more generally dark, and more obscurely striated 

 than any other part. 



Above the last, in the part marked G, the striations become 

 again more distinct, but of a different colour, light yellowish-brown, 

 as at the bottom. 



The thickness of the upper portion of the stone, F and (?, varies 

 from | to | inch. 



III. Its Miceoscopic Chabactebs. 



1 0. " The rock is mainly composed of extremely fine granular calcite, 

 and contains a few very small grains of quartz. In the part which 

 shows the characteristic markings there are patches of clear and 

 sometimes coarse-grained crystalline calcite." l 



11 . The arborescent markings and the stria? are composed of a form 

 of carbonate of lime which takes a higher polish than the mass of 

 the stone. In the specimen shown in tig. 1 (p. 395) they are entirely 

 composed of coralloidal aragonite, whereas in the other (fig. 2, p. 397) 



1 J. J. H. Teall, quoted.in H. B. Woodward's paper, p. 113. 



