298 Messrs. Buckland's and Conybeare's Observations on the 



absence of distinct stratification^ and by the presence of irregular partings 

 and lines of false stratification, running obliquely across thick beds of uniform 

 texture, which afford massive blocks of freestone. In a country, however, 

 where so much better building- stone is at hand, it is seldom employed for 

 architectural purposes ; though formerly used at Bristol in the walls of the 

 cathedral and other ancient edifices, and recently in the construction of the 

 docks. The want of durability of this stone is lamentably attested by the 

 present mouldering state of the cathedrals of Bristol, Chester, and Carlisle, and 

 of the churches at Coventry, the decay being occasioned, in some instances, 

 by the salt or gypsum which the rock contains. Near Ratcliff church, there 

 is a series of catacombs in this rock, resembling on a small scale those of Paris, 

 from which stone has been extracted in ancient time for the buildings in the 

 city. This sandstone may be studied most advantageously in the neighbour- 

 hood of Chew Stoke and Chew Magna, and in the new cut at Bristol. At 

 the latter place a cellular variety of it has been found, the small cavities of 

 which are lined with sulphate of strontia. 



§ 3. Upon the sandstone repose beds of red and variegated marl, which is 

 not laminar like that of the old red sandstone, but globular in structure. The 

 marl in the upper part of the series becomes green, and then contains sub- 

 ordinate layers of red and green marl-stone, approaching in character to lias, 

 and gradually passing into it. The marl sometimes contains nodules, and is 

 sometimes traversed by veins of gypsum and sulphate of strontia. Both these 

 minerals are found in the marl of Aust cliff. The lowest bed of marl is there 

 traversed by tortuous and curiously reticulated veins and beds of gypsum, and 

 is cut by two nearly vertical veins of sulphate of strontia, which is sometimes 

 fibrous. We shall have occasion to revert in the sequel to this cliff, when 

 describing the lias by which the red marl is there covered. It directly faces 

 the opposite cliff of Annards on the right bank of the Severn, where we find 

 a corresponding succession of beds of red marl crowned by lias. In the hill 

 to the north-west of Bitton, and at Tortworth, the marl contains large blocks 

 of sulphate of strontia, which is there called salt-stone. The sulphate of 

 strontia occurs in the same geological situation at Knaresborough in York- 

 shire and on the coast of Glamorganshire. 



The two preceding members of the newer red sandstone formation, the red 

 sandstone and the red marl, are of far inferior interest to the conglomerate, 

 as presenting wherever they occur the greatest uniformity of character ; we 

 refer, therefore, for the details of their geographical extent to the map which 

 accompanies this memoir. 



They are found extensively distributed within the Bristol coal-basin, ap- 



