KiNAHAN — On Canadian Arclman, and Pre- Cambrian Bocks. 357 



William), Sterry Hunt, and otliers, seem to insist tliat they are 

 not only lithological but also geological groups. 



A rock that seems to be considered a typical Ontario Lauren- 

 tian is a pinkish or flesh-coloured fine-grained gneiss, hand speci- 

 mens of which are undistinguishable from some of the fine gneissic 

 rocks of the Cambrians of south-east Wexford (Saltees and Foi^- 

 lorn) ; the Cambro-Silurians of the counties Wexford and Wicklow ; 

 the Cambro-Silurians, county Gralway ; the Cambrians (?) of Erris, 

 county Mayo ; and the Cambro-Silurians, or Cambrians (?) of county 

 Donegal. Some of these metamorphic rocks — as for instance those 

 of Forlorn Point — were evidently at first felspathic, and probably 

 tuffose stratified rocks ; this was probably the case also in many 

 places where similar gneiss occurs in the counties Gralway, Mayo, and 

 Donegal ; but there are also in those places and in the county Wick- 

 low similar gneisses which evidently were originally intrusions of 

 felstone or felsite. In the high ground called Chelsea Mountains, 

 Yale of the Gatineau, Ottawa county, there is a granitoid gneiss 

 very like some of those of Oalway, Mayo, and Donegal ; that is, a 

 rock intermediate in structure between the typical gneiss of Ontario 

 and the gneissic granite of Chicoutimi, Montcalm, &c., province of 

 Quebec — three different rocks, all somewhat similar in constituents, 

 but having been subjected to different degrees of metamorphic 

 action. 



In connexion with the Chelsea district may be mentioned the 

 schistose rocks that occur in the lower ground nearer Chelsea. 

 Associated with these are some peculiar calcareous rocks that are 

 identical with some of the rocks of the " Ophiolyte and Dolomyte 

 series" of the Twelve Pins or Connemara district, county Galway 

 (" Greology of Ireland," chap, i., p. 21). These rocks of Conne- 

 mara have been suggested by King of Gralway, to be of Cam- 

 brian age, and my examination of the country goes to confirm 

 that opinion.' 



It is necessary before we proceed further to mention some pecu- 

 liarities in connexion with certain Irish calcareous rocks. There 

 are, associated with the Lower Carboniferous sandstone of Clare, 



1 These rocks, although undoubtedly some of the very oldest in the county Galway, 

 have not been included in the so-called Archaean rocks ; those called Laurentians 

 being e^ndcntly of newer ago, which has been proved by their fossils to be of Cambro- 

 Silurian age, and have been so classified. 



