Notice of the Address of T. Sterry Hunt. 89 
“Suppose a solution of alkaline silicate, which will never be 
wanting among sediments where feldspar exists, to be diffused 
through a mixture of siliceous matter and earthy carbonate, 
and we have, with a temperature of 212° F, and perhaps less, 
all the conditions necessary for the conversion of the sedi 
mentary mass into pyroxenite, diallage, serpentine, talc, rhodo- 
nite, all of which constitute beds in our metamorphic strata. 
Add to the above the presence of aluminous matter, and you 
have the elements of chlorite, garnet and epidote. We have 
here an explanation of the metamorphism of the Silurian 
a 
altered rocks, will appear in the Report of Progress of the 
It should be added, that Professor Hunt acknowledges his 
change of opinion in his address. But, in view of it, some 
moderating of his positiveness of assertion would have been 
ble. 
reasona 
4. That he attributes the origin of beds of serpentine and 
steatite—here following nearly Delesse,—to the alteration of 
beds of different hydrous magnesian silicates related to-sepiolite 
(meerschaum), formed in the surface waters of an era—Paleozoic 
or earlier—while fossiliferous rocks’were in progress :—when, 
dients from any external source, like most other eee re 
instead of through the agency of outside ingredients. 
eae 
