214 ON THE ORIGIN, MATERIALS, COMPOSITION, 



pressure that might have rendered many earths far 

 more soluble than we know them to be, in what re- 

 mained fluid of that water, thus heated to some un- 

 known temperature. On a speculative opinion of this 

 nature, I need offer no remarks, in an inquiry which 

 rests on better kinds of evidence and probability. 



No notice has yet been taken of the power of mere 

 pressure, either in actually consolidating rocks or in 

 assisting their consolidation. Yet it is an agent not 

 to be overloooked ; and when we consider the enor- 

 mous weight to which the strata must have been sub- 

 jected, it is very easy to conceive that its power can- 

 not always have been inefficient. The occasional 

 compression and fracture of imbedded shells, proves 

 that it has sometimes really acted ; and if even the 

 most delicate of these bodies are generally preserved, 

 it only proves that they were well supported by the 

 surrounding materials, not that they have not been 

 subjected to great pressure. In our own experiments, 

 with forces far inferior, clay can be compressed into a 

 substance as hard as shale ; and there are many of 

 the schists riot so hard as the heterogeneous mixture 

 which is forced into a rocket, though composed of 

 materials from which such an effect could scarcely be 

 anticipated. 



Of the Analogies among different Rocks, and of 

 their Resemblances to unconsolidated Strata. 



Having thus attempted to assign probable causes 

 for the consolidation of the original materials of 

 rocks, it will not be useless to attempt to trace these 

 through their progress ; to inquire if it is possible to 

 discover, in the component parts and disposition of 

 the most antient rocks, any resemblance to the loose 



