212 Capt Huttoris Geological Report [No. 111. 



consideration. The truth therefore of Be la Beche's proposition will be at 

 once established. 



(See plate) — Fig. 5. Let us suppose these now inclined strata to be in their 

 original horizontal position, and 2 and 3 forming beds of unconsolidated 

 sandy and muddy deposits beneath the waters of the lake or sea a c eh. 



Then a a a a, &c. is a vein of lava or molten trap, which in its endea- 

 vours to find vent, upraises and bursts through the solid primary series 

 denoted at 1 . 



By the heat and pressure thus engendered, the lava indurates the sand at 

 2, and converting it into sandstone, breaks through it also, and is thus 

 brought in contact with the muddy deposits represented at 3. This deposit 

 being of a specific gravity inferior to the stream of lava, is naturally dis- 

 placed and forced to contract and furnish room for a stratum of trap 

 at a a a. 



The heat and pressure, however, continuing, speedily and almost on 

 the instant, converts the muddy deposit into shale or slate clay. And 

 the lava current bursting through it and the superior stratum of limestone, 

 comes at length to the surface, and in contact with the waters. Here 

 then commences the facts detailed theoretically by De la Beche, as already 

 quoted, and the stratum of trap spread over the surface of the now inclined 

 and consolidated strata of deposits ; while the waters of the lake or sea 

 being displaced by the upheavement, effected an escape through the 

 various channels afforded by the disruption of the uprising strata. 



It may possibly be objected that the occurrence of a compact stratum 

 of limestone above the shale, and in contact with the trap, will at once 

 invalidate the theory here proposed, from its being a known fact, that 

 when heat is applied to calcareous matter, the carbonic acid is driven 

 off, and the remaining lime rendered infusible. 



I shall endeavour therefore to obviate such an objection, by quoting and 

 establishing a theory long since propounded by Dr. Hutton, which at the 

 time of its proposition was looked upon as an ingenious, but perfectly un- 

 tenable, doctrine. 



" He had asserted that calcareous rocks, like every other, had been sub- 

 jected to the action of heat. But it was well known that when heat was 

 applied to this class of rocks the carbonic acid was driven off in the shape 

 of gas, and the remaining quicklime become infusible. Dr. Hutton in- 

 deed had answered this by suggesting, that the pressure of the superincum- 

 bent ocean was sufficient to confine the carbonic acid, and to cause it to 

 act as a flux on the quicklime. His theory, however ingenious, was so 

 abundantly gratuitous, that it by no means satisfied even his own disciples. 

 After Dr. Hutton's death, Sir James Hall ascertained by numerous experi- 



