20i 
THE GEOLOGIST. 
"Without wicshing at present to go into any discussion of the 
suhject 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 efi'ecting 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 Eoyal 
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 afi'ect 
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 eflects we hare been in 
the habit of assigning to the internal fires. 
ON THE OLDEE PAEIAJST FOEMATION IN TEINIDAD. 
Br E. Lechmere Guppt. 
In the Eeport on the Geology of Trinidad the Government 
geologists described a series of sandstones and shales extending 
across the island from east 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- 
