90 
PALEONTOLOGY OF NEW-YORK. 
Now it seems to me that the proposition here stated, and the result which follows, 
tend to sustain the views I have advanced. 
If this deposit C becomes so great as to disturb the equilibrium of pressure, and 
the effects upon the yielding mass below are such as to displace a portion of the 
same, then the strata which were originally deposited in a horizontal position must 
become curved. The area of deposit could not have acquired an equal accumulation, 
and there would be little or no depression towards the thinning margins. Then if the 
accumulation should go on to many thousands of feet in thickness, and the ocean bed 
be depressed accordingly, we should have a greater deflection of the strata from the 
original horizontal position; and, as I conceive, this depression must be accompanied 
by folding or plication, unless, as Herschel suggests, the support may give way, 
and the mass be plunged into the fluid beneath, which ivould cause a rush of this 
matter upwards. This condition, however, as I believe, happens only when the 
accumulation is very rapid, and probably often not widely extended. 
I am not quite able to agree that the subversion of the equilibrium of temperature 
is more important (in the outset at least) than the subversion of the equilibrium of 
pressure, though I conceive that its ultimate effects are more important and more 
permanent; since, as he says, every continent depressed has a tendency to rise 
again, and, as I understand, this results in a great measure from a restoration of the 
equilibrium of temperature. It is this ultimate rising of continental masses, that I 
contend for, in opposition to special elevatory movement along the lines of moun¬ 
tain chains. 
In a letter to Sir Roderick Murchison, following the one above cited, Sir John 
Herschel discusses this subject still farther, showing conclusively that the deposi¬ 
tion of sediments, subverting the equilibrium of temperature and of pressure, pro¬ 
duces the result, as a natural and necessary consequence, which even at this day is 
too often attributed to excessive or abnormal influence of the heated or fused interior 
mass. u Let strata be deposited ,” he says, and we have all the required condition 
for producing metamorphic rocks. 
Reasoning from a different point, and with a different class of facts under con¬ 
sideration, I have arrived at the conclusions before given; and, farther, that without 
great accumulations of strata ( perhaps a legitimate deduction also from the argu¬ 
ments of Herschel), no important or extensive metamorphism can take place. 
In the preceding pages, I have often used the term current lines, or accumulation along the current lines. I 
might, more properly in most cases, have used the term coast lines or shore lines; these being doubtless the zones of 
great accumulation, and in this view we may have had a coast line nearly parallel and coextensive with the Appalachian 
chain. This fact, however, if ascertained, would not conflict with the facts or arguments I have adduced. 
