li \:1.1:j,\.Kj^. 



rhe t agnetip oxide or protoxide. In the protoxide 

 ^ ill combina 'on in some of the miueral* — the undecoi 



'idote or viri- 

 -18 thoroughly 

 ih a greenish 

 ■'• -■ vMhated 



., ... .1 verv 



dnrk ti^ V 



rs and micaa r such alteration j>rodii 



rati'm comjx). nde, parti eui; 



ut the mass f the rock, imj 



.; .mchanged mic ',, hornblende, a... 



ii'ticies, give the roci « a gray color of ^ a. ...^ . 



;ry light. tVhenever hiese beds have been subject to metamor- 



n. as has often happoc k1, the proto-compounds of iron are often 



lioxide, prot icing a pinkish color similar to that of 



of the tufaceoua beds would enable us 



''>sed of ma! rent from 



iltogether t(.M> ctmspiciioas to admit 

 of any donbt. The origin of these c wtic materials, proximately considered, 

 is in the break up and deatrucl; Ider massive volcanic rocks by the 



ordinary pre- ndeed, possible that some small 



t material blow;: 



j liie strata ao- 



. "i the tnffuj did'i'H -.. 



iiier matei'-'d r,.,ii..i-.t from 



t tliat they hris of 



Inanui instances 



lisonta res, by a gradual transition, 



>i materia) derived from the 



>mirjg : less, while th;U 



d Hum tLi •" ocks b«x«»uie8 greater and 



•r. Instan( itioi) n "i varioti»i parts of the Sevier 



aiaudiut! ,?.. r.  the Marbigunt. Indeed, I 



•: not that th. mo-t tvni.'Mllv " tiiffif.-rms," 



