178 



In the great coal district near Cologn, not only the 

 trunks of trees, deprived of their branches, are found, 

 but " nuts which are indigenous to Hindostan and 

 China, and a fragment of a resinous guin are also found 

 in it."* 



To the operations of these currents we may attribute 

 the cause of the excavation of the rocks at Gibraltar, 

 as mentioned by Major Imrie, " On the surface of the 

 rock," he observes, "are seen pot-like holes, hollowed 

 out by the attrition of gravel or pebbles, set in motion 

 by the rapidity of rivers, or currents in the sea, some 

 of the pebbles now remaining in them." 



From this phenomenon Mr. Imrie concludes, that 

 f( however high the surface of this rock may now be ele- 

 vated above the level of the sea, it has once been the 

 bed of agitated watersS'-\ 



Admitting these facts to be true, do we hazard too 

 much in saying, that, probably, at the same epoch, in 

 which these holes were formed, the great and impor- 

 tant event took place, which the ancients have so often 

 mentioned, and of which so much has been said, (viz.) 

 the disjunction of Europe and Africa by "the labours 

 of Hercules" so called :f and by which a communica- 

 tion was opened between the Mediterranean sea and 

 Atlantic Ocean, at the straits of Gibraltar ? 



Whether this be true or not, it is worthy of remark, 

 with respect to the excavations, or pot-like holes in 



* BakeweH's Introduction to Geology, page 197. 

 t Parkinson's Organick Remains, vol. Ill, page 332 

 \ See Natural History of Pliny, book 3. 



