Igneous Hjections, Volcanoes. 109 
allows of the movements observed in the solid crust. 
It will be perceived that the hypothetical viscous layer of 
Hunt lies between a rind made out of sedimentary formations 
and a solid nucleus which is at surface of sedimentary origin ; 
and the viscous layer which Professor Hopkins regards as be- 
longing to a stage in the process of solidification is supposed to 
have been closed up, or some way put ‘“ hors de combat.” 
This substitution appears to be quite unnecessary, and the 
process incapable of producing the result claimed. As has been 
already explained,+ the pressure from the gravitation of sedi- 
ments cannot produce the heat needed for the fusion, no more 
than it can cause the plications alleged to attend it. If then 
no fusion of sediments would have resulted from such a cause, 
there was no chance for the formation of the deep and extended 
plastic zone required to meet the demands of the grand system 
of oscillations the earth’s surface has experienced. In fact, the 
conditions Prof. Hunt’s hypothesis appeals to—that is, thick 
sedimentary accumulations, such as those of the Appalachian 
region,—are far too local for the production of so vast a plastic 
zone, even if fusion were a possible result of the accumulation. 
Again, the facts mentioned on the preceding page give as 
positive a declaration against this origin of the material of 
igneous ejections through the fusion of sediments. The sedi- 
mentary strata along the Atlantic border, whether unaltered or 
metamorphic, deep-seated or superficial, vary every score of 
_ miles, and could not yield a uniform quality of fused material 
for the ejections. In the Connecticut Valley the metamorphic 
rocks from New Haven, Conn., to northern Massachusetts, a 
Archzean (Azoic) rocks to the west, in Dutchess Co., N. Y., and in 
Connecticut west of Winsted, are diverse varieties of gneiss anil 
granitoid gneiss, containing orthoclase and albite or oligoclase 
with quartz, and sometimes hornblendic, but as far as known 
the last rock to be looked for from any of it, except it be from 
* Geological Magazine, Feb., 1868. + This vol., page 13. 
