252 Dr Hibbert on the Limestone of Burdiehouse, 



are still operating, meet with even a less adequate explanation, 

 unless they may be compared with the tranquil elevations of land 

 which have been long going on in Scandinavia, or with the com- 

 paratively trifling oscillations of movement which have been de- 

 tected on the well known site of the Temple of Jupiter Serapis. 



In short, no geological phenomena are more striking than the 

 alternations of fresh water and marine beds which are manifested 

 in strata, such as those which I have described. 



The carboniferous strata of the Gracemount and Burdiehouse 

 systems, may be summed up as follows : 



The lower beds comprise sandstones of considerable thickness, 

 alternated, as we ascend in the series, with argillaceous or bitu- 

 minous shale, and with limestones, some of which give indications 

 of a marine, and others of a fresh water origin ; the latter con- 

 taining remains of plants and fish. Coal begins to be developed 

 in these beds, though sparingly. 



In a second, and higher description of beds, the sandstone al- 

 ternates more frequently with beds of argillaceous and bitumi- 

 nous shale ; the latter containing nodules or bands of ironstone, as 

 well as seams of coal, which, though numerous, are, with few ex- 

 ceptions, thin and unworkable. These higher strata are particu- 

 larly interesting for the renewed development of a limestone con- 

 taining marine remains, with which they alternate. 



In a third description of beds, which take a still higher place 

 in the carboniferous system, sandstone and argillaceous shale al- 

 ternate with rich seams of coal, of which about twenty-five have 

 been enumerated. 



From this summary it appears, that these alternating beds con- 

 sist of sandstone, shale, coal, a fresh- water and a marine limestone. 

 Their separate character I shall briefly discuss, previous to inves- 

 tigating the circumstances of their alternation. 



Deposits of sandstone, which are the disintegrated materials 

 of previously existing rocks of a siliceous character, have no doubt 



