204 



THE GEOLOGIST. 



"Without wishing at present to go into any discussion of the 

 subject of central heat, we can but rejoice at the acquirement of this 

 evidence of the former sedimentary origin of this highly metamor- 

 phosed rock ; and we sincerely hope that it will not be long before 

 we have more proofs of the like nature. Heat may have had much 

 influence in effecting metamorphic changes, but we think it far more 

 likely that water, mechanical pressure, and chemical action have been 

 the principal workers in metamorphic action. The curious sections 

 of encrinital limestone which Mr. Sorby exhibited at the last Royal 

 Society soiree, showing how mechanical pressure and chemical 

 action had caused the solution or removal of the material of the en- 

 crinital joints on the one side, while on the other deposits of other ma- 

 terials had taken place, gives indication how such processes could affect 

 rock-masses on a large scale; and while geologists are demanding 

 heat to reduce to a pasty condition our metamorphic rocks, why, we 

 would ask, might net such mechanical and solvent actions, by remo- 

 ving obstructions to motion on the one hand and permitting a deposit 

 of material on the other, be a slow but sure way of bringing the 

 integral particles of rocks into crystalline forms or into parallelism 

 with each other, so that every form of metamorphism, and even slaty 

 cleavage, might be thence produced ? 



By natural and existing phenomena we should attempt, in the first 

 place, to elucidate geological conditions. Cold water is much more 

 abundant than hot ; it does a great deal. We have no real know- 

 ledge now of any deep-seated dry heat-action going on. We may 

 imagine such ; but I much doubt if the mechanical, chemical, and 

 crystalline forces, combined with the solvent power of water, are not 

 quite sufficient to produce very many of those effects we have been in 

 the habit of assigning to the internal fires. 



ON THE OLDER PARIAN FORMATION IN TRINIDAD. 



Br R. Lechmere Guppy. 



In the Report on the Geology of Trinidad the Government 

 geologists described a series of sandstones and shales extending 

 across the island from cast to west, and occupying an extent of about 

 97 square miles. The distribution of the formation, which has been 

 named the " Older Parian," is in the manner of an irregular band of 

 from 1 to 4 miles in breadth, traversing the island in an easterly 

 direction from the Gulf of Paria at Pointe a Pierre. This band ter- 



