FOUND IN SEAMS OF COAL. 



735 



Nook and Burnt Hills Coalpits, in the same district, and at Higher 

 Dog Hill, Oldham. They are also said to occur in the neighbourhood 

 of Leeds. 



The boulders in every case are isolated. Sometimes they occur 

 in the bed of coal, and sometimes at its junction with the over- 

 lying rock. The boulders or pebbles, in the instances I have 

 seen, are invariably waterworn and rounded. 



Two possible explanations of the occurrence of boulders in this 

 anomalous position may be suggested, namely, transportal by being 

 entangled in the roots or branches of trees, and the agency of floating 

 ice. It is by the latter means, I think, that the boulders observed 

 were in all probability conveyed to the spots where we now find 

 them. The chief evidence in its favour consists in the presence of 

 rocks brought from a distance, and the apparent absence of local 

 rocks. 



