372 -_ E. Hitchcock on the Metamorphism of 
Art. XXXIV.—On the conversion of certain Conglomerates into 
Taleose and Micaceous Schists and Gneiss, by the Elongation, 
_ Flattening and Metamorphosis of the Pebbles and the Cement; by 
Prof. Epwarp HitTcHcock. 
important bearing upon that most difficult subject of geology— 
etamorphism,—for they show most conclusively the plastic 
condition of this conglomerate and the associated schists and 
gneiss, subsequent to their original consolidation. Other strong 
arguments do, indeed, lead to the same conclusion: such as the 
change exhibited by the Azoic rocks from a mechanical to a crys- 
talline condition, the complicated foldings and contortions of 
these rocks, the remarkable curvatures of the veins of granitic 
rocks; and the existence of superinduced structures, such as no 
mere mechanical forces could have produced. But I pass by all 
these proofs now, and present only that from the changes in cer- 
tain conglomerates. 
So far as my knowledge of geological literature extends, the 
facts, and some of the conclusions presented below, are mainly 
new ; ‘and this is the chief reason why I offer them to this Jour- 
nal. Professor Sedgwick has, indeed, described joints that “ have 
actually cut through the pebbles of quartzite and other hard 
masses which enter into the composition of the conglomerates.” 
(British Paleozoic Rocks, p. xxxvi, Introduction.) But he does 
to the joint in the Rhode Island or Vermont conglomerates. 
same thing is described by Jukes, in his Manual of Geology, 
more fully. He also notices as an effect of cleavage, the “ distor- 
tion of fossils and other small bodies imbedded in the rocks, 
lengthening and pulling them in the direction of the cleavage and 
contracting them in the opposite direction.” These facts, first 
= particles of rock in one 
hes om 2 
monize with these views and lead to generalizations still 
especially to the position so ably defended by Scrope, Bi 
