in the Neighbourhood of Edinburgh. 259 
own finny monsters, which, in pursuit of their prey, would pene- 
trate into fresh-water lakes, and even among the shallows of 
marshes. 
These speculations may be extended to newer deposits. 
In the strata succeeding to the Burdiehouse limestone, which 
consist of alternating beds of argillaceous or bituminous shales, of 
sandstone, and of thin seams of coal containing both vegetable 
and animal remains, we find that the calcareous deposit of 
Burdiehouse was but a temporary elaboration. 
At Fountain-well, a thicker seam of coal (now wrought out) 
was once evident, covered by a bed of limestone, which contains 
marine shells, encrinites, corallines, &c. In reference to this, as 
well as to similar limestones of the south of Scotland, I may ob- 
serve, that if the geologist expects to find these deposits of the 
same thickness as many in England, he will not fail to be disap- 
pointed. They occur in beds, perhaps not at the utmost more 
than forty or fifty feet thick, except im some places, and often 
alternating with sandstone and argillaceous shale. It is also re- 
markable, that not unfrequently three distinct alternations of 
this limestone will be found, as I have noticed between Mussel- 
burgh.and Prestonpans. These alternations certainly indicate. 
that fresh-water lakes, or marshy tracts, were liable to be sub- 
merged by shallow seas, and not to be overwhelmed during a very 
prolonged interval beneath the waters of a deep ocean. 
Phenomena of this kind are calculated to excite the greatest 
possible interest. They may be considered as affording unequi- 
vocal proof of the gradual, but momentous geological agency, which 
has been in operation. Partly from changes of level, occasioned 
by the internal commotions of the globe, and partly from cir- 
cumscribed and local circumstances, new seas have in succession 
overflowed much of the land which had hitherto been the site of 
dense marshes, or tanks. The proof of these phenomena subsists 
in the beds of encrinal, coralline, and conchiferous limestones, 
Kk2 
