242 The Ottawa Naturalist. [March 



istic of mountain formation and also examples of forms which are 

 repeated over and ov^er again in other mountain rang'es of the 

 world. As the foundation of the subject as treated in the lecture, 

 the parallel was drawn between mafi in his artistic productiona 

 and Nature in her fashioning^ of existing mountains. The lecture 

 thus fell into three divisions corresponding to Nature's activity as 

 an architect, as a sculptor, and as a painter. 



The raw material with which Nature works in mountain- 

 building is derived from stratified rock-material originally deposited 

 in thick and extensive layers on the sea-floor. The methods by 

 which the once flat-lying s ibmarine strata are elevated into a 

 mountain-range, include the folding and faulting of those beds, 

 due to great lateral pressure at right angles to the axis of the 

 range. In the process of folding, the width of the belt of rock so 

 engaged i.s diminished and the thickness is correspondingly in- 

 creased. As one consequence the lower parts of the greater folds 

 become so deeply buried as to feel the influence of subterranean 

 heat and of hot water and gases circulating within the earth's 

 crust. The folded marine strata are in this way subjected to alter- 

 ation and crystallization : from them many kinds of crystalline 

 schists, so characteristically developed in great ranges throughout 

 the world, have been derived. Again, the mountain folds may be 

 partially displaced by molten granite or allied rock-material 

 rising from the earth's interior and invading the overlying forma- 

 tions The importance of this ki id of raw material used by Nature 

 in producing her mountain architecture, is recognized by the 

 tourist visiting, for example, the Yosemite Valley, perhaps for its 

 area affording the grandest bit of scenery in the world. The 

 " central granites" of most great mountain ranges usually furnish 

 much of the scenic magnificence of those ranges. Finally, the 

 fractures opened by folding and faulting in the rocks composing a 

 range, may permit of the overflow of molten rock from subter- 

 ranean sources ; tae result has been to form in the west, Mt. 

 Baker, Mt. Rainier and other huge volcanoes, among the 

 grandest units in the scenery of the Rocky Mountain Region. In 

 summary, folding, faulting, metamorphism, granitic intrusion and 

 volcanic eruption were briefly noted as the methods by which 

 mountain architecture has been determined. 



