MACKIE — THE llOCRS AND TllElR TEACHINGS, 



continually over tlie same ground, attain to a perfect Utidci'staiidiug of 

 the subject of his study. He must go abroad, either in his o'nVH |)Oi-sojl 

 or equivalently, by making himself acquainted with the travels aJl(i 

 labours of others. Our knowledge of the ancient conditions and 

 relations of the oldest rock-masses would not be complete if wc limited 

 our investigations to tiiose isolated patches in our own country, which, 

 however important, are still only a part of that great whole, more 

 important traces of which are to be met in regions far away. Tlius 

 those very old — indeed, primitive sedimentary rocks, represented in the 

 British Isles in a fragmentary manner, as by the younger or bedded 

 gneiss of the Scottish llighlands, assume in Canada and the Arctic 

 regions proportions of great extent, and consequently, of far greater 

 value. Par back in the obscurity of tlie past, as must be placed tlic 

 birth-time of these primitive land-masses, wc seem, in our first 

 investigations, plunged in interminable ignorance, like the explorers of 

 some vast subterranean cave in impenetrable darkness. Wc leave tlic 

 clear evidences of phenomena around us, as we leave the bright sun- 

 phinc and the miles and miles of gilded landscape vivid through the 

 transparent air. All is blank, void ; we know not where to tread ; the 

 eye is strained in its efforts to peer through the obscurity until it begins 

 to detect, one after another, the slender threads of light that, peering in 

 through the cracks and fissures of the roof and walls, are faintly reflected 

 from objects around, and in the end we g-iin a comprehension of the form 

 and grandeur of the cavity. 



But the evidence of the primitive lands is not in hopeless obscurity; 

 there may, indeed, be dark and intricate passages, but the broad light of 

 Heaven shines on a great deal, and in the mountain-ranges of the world, 

 often stand out, bold and high, the memorial pinnacles of the first dry- 

 land. There is nothing, in reality, to prevent us, by labour and per- 

 severance, obtaining a just and accurate conception of the earliest stage 

 of the terrestrial and aqueous conditions of our planet, at or before the 

 first traces of that succession of animal and vegetable life, v/hich, 

 repeatedly adapted to its ever varying fitalep, has descended through 

 numerous m.odifications to our own days. 



Wo have learned, already, to distinguish the granites of various 

 ages, from primeval to tertiary, from each other ; and we have now 

 learned to assort the older or unbedded gneiss, from the younger or 

 bedded gneisc — the former a portion of the firf^t world, the hitter the 



