ADDRESS. 13 



must go back to a time when the areas occupied by the Atlantic and 

 its bounding coasts were parts of a shoreless sea in which the earliest 

 gneisses or stratified granites of the Laurentian age were being laid 

 down in vastly extended beds. These ancient crystalline rocks have been 

 the subject of much discussion and controversy, and as they constitute 

 the lowest and probably the firmest part of the Atlantic sea-bed, it is 

 necessary to inquire as to their origin and history. Dr. Bonney, past 

 President of the Geological Society, in his Anniversary address, and 

 Dr. Sterry Hunt, in an elaborate paper communicated to the Royal 

 Society of Canada, have ably summed up the hypotheses as to the origin 

 of the oldest Laurentian beds. At the basis of these hypotheses lies the- 

 admission that the immensely thick beds of orthoclase gneiss, which are 

 the oldest stratified rocks known to us, are substantially the same in 

 composition with the upper or siliceous magma or layer of the under- 

 crust. They are, in short, its materials either in their primitive condition 

 or merely rearranged. One theory considers them as original products 

 of cooling, owing their lamination merely to the successive stages of the 

 process. Another view refers them to the waste and rearrangement of 

 the materials of a previously massive granite. Still another holds that all 

 our granites really arise from the fusion of old gneisses of originally 

 aqueous origin, while a fourth refers the gneisses themselves to molecular 

 changes effected in granite by pressure. These several views, in so far 

 as they relate to the oldest or fundamental Laurentian gneiss, may be 

 arranged under the following heads : (1) Endoplutonic, or that which 

 regards all the old gneisses as molten rocks cooled from without inward 

 in successive layers.^ (2) I^xoplutonic, or that which considers them as 

 made up of matter ejected from below the upper crust in the manner of 

 volcanic action.^ (3) Metamorpldc, which supposes the old gneisses to 

 arise from the crystallisation of detrital matter spread over the sea-bottom, 

 and either igneous or derived from the decay of igneous rocks.^ (4) 

 Chaotic or Tliermo-chaotic, or the theory of deposit from the turbid waters 

 of a primeval ocean either with or without the aid of heat. In one form 

 this was the old theory of Werner.* (5) Crenitic or Hydro-thermic, which 

 supposes the action of heated waters penetrating below the crust to be 

 constantly bringing up to the surface mineral matters in solution and 

 depositing these so as to form felspathic and other rocks.^ 



' Naumann, Phillips, Durocher, McFarlane, <fcc. 

 ^ Clarence King, Tornebohm, Marr, kc. 

 ' Lyell, Kopp, Eeusch, Judd, &:c. 



* Scrope, De la Beche, Daubree. 



* Hunt, loo. cit. The following is Dr. Hunt's summary statement of this theory ; 

 ' The globe consolidating at the centre left, it is conceived, a superficial layer of basic 

 silicates, which has yielded all the fixed elements of the earth's crust. This layer 

 formed the first land and the floor of the primeval sea, the acid waters of which 

 permeating and partially decomposing it, became thereby chemically neuDralised.. 

 This last-cooled layer, mechanically disintegrated, saturated with water, and heated 



