Descent and Upheaval over the Northern Hemisphere. 327 



covered over with a deep layer of alluvium in the valley of 

 the Carse, and at Perth. Similar deposits occur at Mounts 

 Bay in Cornwall, in Lincolnshire, and in Orkney. In 1837, 

 in a report drawn up for the Highland Society, on the geology 

 of the southern portion of Perthshire, I specially adverted to 

 the circumstance of the occurrence of the beds of cockle-shells 

 under the silt, and above the peat and tree roots which seemed 

 to me only capable of being explained on the hypothesis that 

 when the trees grew in the position now occupied by their 

 roots, the surface of the land must have been, at least, ten 

 feet higher than at present, so as to have placed them above 

 the tide : — that a subsidence of, at least, twenty feet must 

 have occurred, and that during this period the cockle-bed had 

 come into existence ; and, as the earth continued to descend, 

 became buried in the mud which now covers it to the depth of 

 ten feet. That the movement must have next changed its 

 direction, raising the cockle -bed at least ten feet above its 

 original position, bringing the Carse of Gowrie sixteen or 

 twenty feet above the sea, and elevating the tree-roots to 

 low- water mark. 



9. The phenomena around us here, in Western India, 

 exactly correspond with those of the Carse of Gowrie. The 

 whole of our littoral formations consist of the concrete already 

 alluded to, or of loose sand and shells. From three to ten 

 feet under this — the depth varies — is a bed of blue clay, 

 exactly similar to that with which our estuaries are being 

 silted up. In a great majority of cases the blue clay is filled 

 with the roots of the mangrove, a shrub which only grows 

 within high-water mark, avoiding water of more than four or 

 five feet deep. The fangs and fibres of the roots are per- 

 fectly entire, some of the thickest of them, indeed, are but 

 imperfectly decomposed, most of them are converted into a 

 substance like peat, and, when dried, break with a conchoidal 

 fracture and semiresinous texture, something between jet 

 and lignite. These roots and their arrangement is found 

 to prevail all d^round the island of Bombay, on many parts of 

 the shores of the island of Salsette, on the shores of the Gulf 

 of Cambay, and at Kurrachee in Scinde. This state of things 

 is not peculiar to creeks, bays, or estuaries, and can in no way 



