160 Conglomerates in Gneissic Ter rams — A. Winchell. 
cited in reference to the Saganaga pebbles are simply corrob¬ 
orative of views supported by other classes of evidence on which 
I do not here enlarge. Though merely touching the general 
problem of the origin of gneisses and granites, I wish to avoid 
all misapprehension by stating that I recognize the important 
agency of heat in connection with water, in the transformation 
of the original sediments; I do not conceive that the charac¬ 
teristic features of these terranes are any legacy of sedimentary 
conditions; but I hold, with Scrope, de Beaumont, Scheerer, 
Hunt and others, that the primitive materials, through the 
agency of heat, water and chemism, have entered into combina¬ 
tions not existing in the original sediments. I hold that the 
transformation attained different degrees of completeness in 
different localities and different horizons; and I hold that pres¬ 
sure—especially shearing pressure—has emphasized the bedded 
arrangement. Thus, as I believe, the sediments were brought 
to a state of incipient crystallization in one place, and completer 
crystallization in another; while in others, the thermal action 
•was intense enough to reduce the magma to a state of such com¬ 
plete fluidity or plasticity as to obliterate all traces of bedding, 
or allow squeezing into fissures, or even surface overflows of any 
such extent as observation may establish. I wish to add the 
important suggestion that the agencies which would transform 
the common magma would also transform the included pebbles. 
By softening and pressure, their forms have been changed; and 
by metamorphic action they have ceased to present, in some 
cases, their original mineral constitution. 
Such views on the history of crystalline masses though not 
widely entertained, will be found supported by considerable 
evidence of the same nature as that afforded by the pebbles and 
conglomerate of the Saganaga gneiss. In 1833, Professor 
Edward Hitchcock called attention to certain features of a con¬ 
glomerate occurring near Newport, Rhode Island. J The pebbles 
showed evidences of a former softened state, and of a partial 
transformation, in certain cases, to “a mica schist with a cement 
of talcose slate.” Similar conglomerates were described by Dr. 
* Fif teenth Ann. Hep. Minn., 1880, p. 264. 
+ Sixteenth Ann . Rep. Minn., 1887, p. 264. 
% E. Hitchcock, Report on the Geology of Massachusetts, 1838. See also, 
the Reports of 1833 and 1841. The same was more particularly described 
by Professor C. H. Hitchcock in Proceedings Amer. Assoc., I860, pp. 112-118. 
