The iRox-r.KAiMxc m K:\ir.Ki;. 245 



in niajinetit«\ Tlic led mikI lnown l;iiiiiii;r art' iic:nly (i|i;i(|iic itssrefiatidiis of 

 particles of hciuatite and liy(lroscs(|iii()\i(li'. Tlic i^iccnisli haiids arc imrtictilaily 

 rich ill actiiiolite. The siliceous grouiidmass is rehitivcly not ahiiiidaiit. but nms 

 tlii(Hij;iioiit tlie section. The bandinij of this rock is taken to be deiiciideut n|)oii an 

 orii;iiial sedimentary hiiuination, but llie way in whicli tlie liands aie seen now to be 

 swollen, iiiinuiely cont(U-ted, or abruptly inokeii ott' is a stroiiy- indication of tlie second- 

 ary origin of a portion of the minerals which are now pi-cseiit. liesides following 

 the original lamination, the various groupings of the minerals Inive often tra\ersed 

 this lamination. One traversing seam of actinolite and silica is j)articularly note- 

 worthy. This is a structure which can hardly l)e described, but is of importance in 

 its l)earing upon tlie origin of these singular fernigiiions rocks. 



SECTION II.— ORIGIN OF THE ROCKS OF THE IRON-BEARING MEMBER.' 



Knowing the exact tacts as to the nature and inetlnMl ol' occurrence of 

 the iroii-bearino- rocks, we are now prepared to jiresent some consistent 

 account of tlieir orioiu. In the detailed tabuhitions and in the a'eneral 

 account of their macro.scopic and niicroscoiiic cliaracters, it lias been 

 necessary to anticipate, to some extent the orig'in of cei-tain phases. To 

 the degree that tlieir genesis has tlins been anticipated it is not in the 

 nature of tlieory, but fact, because tlie stages of their development to this 

 extent Iia\ »■ actually been observed. Hetore attempting to give a hi.storv of 

 the rocks, it will perhaps be well to recapitulate the more iuijiortant of the 

 observed facts. 



(1) The Iron-bearing member throughout most of its area gives abso- 

 lutely no evidence of a fragmeiital charactei-. This characteristic is one of 

 the greatest importance. The ([uartz rocks of the iron-bearing, belt have 

 been confu.sed with the underlying ipiartzites. H\ most observers tlie\' have 

 been taken to Vie frag-mental, and have been su))po.sed to have reached their 

 present condition liy one of the \ari(uis nnsterious processes of uietauior- 

 phisni. It has, however, been seen that the fragmeiital character of the 

 underlying quartzites and the overlying slates is manifest when their thin sec- 

 tions are exaniineil with a microscope. Xow, tliis Iroii-bearino;- meml)er Hes 

 between these two fragmeiital belts, and yet nowhere in its typical rocks is 



'Section I was nearly completed when Prof. Irving's sudiiiu ilialU nrriirnil. I'ldiii the Ijejjin- 

 ning of this section the Junior author is aloue re8i)(insil)le tor I In- liiri]!, although luiuh of the 

 substance of Sections II and III is Prof, irviuif's work. 



