« THE LAKE OP STENNIS. 



Conglomerate could have accumulated over tracts of sea- 

 bottom from ten to fifteen thousand square miles in area, to 

 its present depth of from one to four hundred feet. At 

 length, however, a thorough change took place ; but we can 

 only doubtfully speculate regarding its nature or cause. The 

 bottom of the Palaeozoic basin became greatly less exposed. 

 Some protecting circle of coast had been thrown up around 

 it ; or, what is perhaps more probable, it had sunk to a pro- 

 founder depth, and the ancient shores and streams had re- 

 ceded, through the depression, to much greater distances. 

 And, in consequence, the deposition of rough sand and rolled 

 pebbles was followed by a deposition of mud. Myriads of 

 fish, of forms the most ancient and obsolete, congregated on 

 its banks or sheltered in its hollows ; generation succeeded 

 generation, millions and tens of millions perished myste- 

 riously by sudden death ; shoals after shoals were annihi- 

 lated ; but the productive powers of nature were strong, and 

 the waste was kept up. But who among men shall reckon 

 the years or centuries during which these races existed, and 

 this muddy ocean of the remote past spread out to unknown 

 and nameless shores around them 1 As in those great cities 

 of the desert that lie uninhabited and waste, w^e can but con- 

 jecture their term of existence from the vast extent of their 

 cemeteries, we only know that the dark, finely-grained 

 schists in which they so abundantly occur must have been 

 of comparatively slow formation, and that yet the thickness ot 

 the deposit more than equals the height of our loftiest Scot- 

 tish mountains. It would seem as if a period equal to that 

 in which all human history is comprised might be cut out of 

 a coiner of the period represented by the Lower* Old Ked 



* [It is the opinion of Sir Eoderick Murchison. that what had hitherto 

 been considered the lowest of the Old Eed occupies the middle place in 

 that fornaation ; likewise, that the whole three formations are represented 

 in Orkney. — See Appendix, B.] 



