J. D. Dana on the origin of the Earth's Features. 205 
In the pradieen of such, I have tote necessarily obliged here 
confine myself to the affirmative side of the question, in suppor ort 
of the existence of a physical image, distinct from chemical re- 
a and though often accompanied by it, yet never “e6ae 
sa 
I cannot conclude these Shor a expressing my 
thanks for the kind assistance given me by my friend Mr. 
Thomas P. Shepard of Providence, Rhode. Island. 4 
Philadelphia, July 10, 1866. : 
ArT. XXX.—Observations on the el li eat of the Earth's 
Features ; by JAMES 
sions are the following: that the deposition and rnc Bs 
large accumulations of sediment produce the folding and c 
pression of strata; bx the alteration or eehadiorpliten of wedi 
ments has arisen primarily from pein geo “this force being 
resolvable into oukek actions that give rise to phenomena which 
seem to be due to heat and to chemical action;” and that “it is 
better philosophy ” attribute the results of of metamorphism to 
this cause “than to a supposed central mass of fluid, gaseous 
emanations, and the like, that we know sthing about, which 
seem oppos osed by important facts, and which, from all we know, 
should act generally and not locally ; oe especially not in the 
regions of great accumulation which from their very thickness 
would seem to be most removed from is source of heat beneath 
the earth’s crust.” (p. 133. 
* For the writer’s earlier discussions of this subject, see volumes ii, iti, iv, ps 
cy Pk this Journal, second series, the writer's Expl. Exp. Geologieal Report, 
Am. Jour. Sc1.—Szconp Srrigs, VoL. XLII, No. 125.—Szpr., 1866. 
