APPENDIX. 545 



gular declivities, which gradually descend to the water's 

 edge." Captain Back remarks, that a point which forms 

 the western extremity of a small bay, in this part of 

 the lake, consists of a mass of boulders, cemented into 

 a kind of puddingstone by yellowish and indurated 

 clay, to a height of from six to forty feet : the subja- 

 cent rocks, as they receded from the lake, acquiring 

 an altitude between 1 400 and 2000 feet. 



The point which we next rounded was steep and 

 perpendicular; and from it the natives obtain a varie- 

 gated marl, of a greenish grey colour, of which they 

 make their calumets and pipes. A similar substance, 

 of a reddish tint, and also one of a pure white, both 

 admitting of a high polish, are found beyond the 

 western limits of the lake. 



Proceeding to the north and east, along that portion 

 of the lake which separates the long island of Peth- 

 the-nu-eh from the northern main, the island itself has an 

 imposing appearance; its rocks, of the trap formation, ex- 

 hibiting long lines of mural precipices, resting one upon 

 another, and capped by even and round eminences thinly 

 clad with meagre pines. " It was impossible to look at 

 them without being forcibly reminded of the same ap- 

 pearances, but without trees, seen on a former occasion 

 between the Coppermine River and Point Barrow, 

 where the rocks are described by Dr Richardson* as con- 

 sisting of clinkstone, porphyry, and earthy greenstone, 

 which extended to the mouth of WenzePs River." And, 

 from this resemblance, Captain Back conjectures that 

 the trap formation may probably run in a line almost 

 due south to Great Slave Lake, where it is lost in the 

 granitic district occupying an extensive range to and 

 beyond Chipewyan. 



* Franklin's First Voyage, Appendix, p. 530. 



N N 



