i v " A. C. LAWSON — RELATIONS OF THE A in II i: AN OF I W \I»A. 



of net nt years, establishiug such an origin for the hulk of the serpentines 

 nt present known the world over. 



There is :i great variety of fissile, more or lees glossy, rather soft, green 

 schists, partly hornblendic and partly chloritic, the origin of which in some 

 cases is closely fixed from the fad that they form the matrix of well char- 

 acterized pebble and bowlder conglomerates. In this case they must have 

 been composed of epiclastic or pyroclastic material. The writer inclines t<> 

 the opinion that they are of proximately pyroclastic origin from the fact 

 thai precisely similar schists, free of pebbl< -. are frequently associated with 

 massive or only slightly Bchistose diabas< s, as if the tuffi of these extravasa- 

 tions. There are many other bedded green schists some of which can he 

 shown to be squeezed and otherwise altered facies of diabase, while the 

 precise origin of others is yet quite obscure. 



The porphyroid schists, the felsite schists with quartz grains, and many 

 of the nacreous sericite schists, represent squeezed, schistose and otherwise 

 altered forms of quartz-porphyries ami petrographically allied rocks, and 



their tuffi, winch, as before stated, enter not un< imonly into the composition 



of the volcanic portions of normal Paleozoic series. Some others of the 

 sericitic schists may probably have been developed from sediments rich in 

 orthoclasc dehris : hut this, except where they pass over into rock- of the 

 character of phyllites, is not so easily established as the direct derivation of 

 many of them from the acid volcanic rocks. 



Original Characters and Metamorphism.—From the foregoing statement, 

 brief and incomplete as il is, of the broad lithological characters of the forma- 

 tion- which constitute theOntarian system, or upper division of the Archean, 

 it must he apparent that, although there are rucks within it whose hi-tor\ is 



more or less obscured by the changes which they have undergone, the system 

 i- an assemblage of once normal rocks, all of which may he found even in 

 their in. .-t altered phases in series of Paleozoic and later ages. This conclu- 

 sion will not appear startlingly new to the very powerful school of American 



who have always claimed the met amorphic derivation of the whole 



of the Archean from normal rocks. 



But, a- will appear in the Bequel, the metamorphic explanation of the 

 whole of Archean phenomena is not tenable, and is only applicable, in the 

 opinion of the writer, to \i< upper division, here designated the Ontarian 



stem. Moreover, ii is to he noted that the conclusion in question oners an 

 important modification of the old view of the metamorphic development of 

 such rocks a- constitute this system, inasmuch a- volcanic formation- have 

 scarcely been recognized in our leading American text-books as having a 



-hare in the composition of the older rock -> ries. Much of the Archean was 



properly recognized a- the alteration product- of sediments, and the whole 



complex was therefore inferred or supposed to In- of similar derivation from 



