APPENDIX. 561 



Cream-coloured limestone, effervescing slowly, containing 

 impressions of shells, and occasional nests of crystallised 

 magnesian carbonate of lime, and in some places stained 

 with bitumen * : found in horizontal strata on the bank of the 

 river. This rock much resembles some of the specimens 

 from the "Ramparts" on the Mackenzie River — Dr. 

 Richardson's list, Nos. 148 — 156. p. xxxiv. xxxv. ; and 

 from Lake Winnipeg, No. 1014. p. liv. 



Great Slave Lake. — Hard slaty limestone, efferves- 

 cing very slowly. " From an island of large extent in hori- 

 zontal strata." Compare with Richardson's, Nos. 60. 132. 

 p. xxxi. ; 205. p. xliv. ; 246. 293. p. vi. 



From Christie's Bay (Peth-the-nu-eh). — Slaty (mag- 

 nesian) limestone, with a vein of sparry magnesian carbonate 

 of lime. Compare with Dr. Richardson's, No. 228. p. v. 

 from the mouth of Dease's River, head of Great Bear Lake ; 

 and 208. p. xiv. from Cape Parry. 



From a small bay in Gah-hooa-tchella. — A speci- 

 men, which formed part of a boulder, found loose on the 

 beach by Mr. King the surgeon of the expedition, consists 

 of limestone, effervescing copiously, and exhibiting on the 

 decomposed surface concretional grains like some varieties 

 of oolite ; and containing also portions of a fossil, the external 

 structure of which resembles the genus Stromatopora of 

 Goldfuss. 



Among the specimens which have an organised structure, 

 probably from the shores of this lake, is one with a tuber- 

 culated surface, composed of calcareous matter, which Mr. 

 Lonsdale considers as belonging to the genus Stromatopora 

 of Goldfuss, and probably to his species pohjmorpha (Plate 

 LXIV. fig. 8. d.) 



* This occurrence of bituminous matter in limestone, nearly border- 

 ino- on a large tract of crystalline and igneous rocks, may deserve atten- 

 tion with reference to the hypothesis of Dohmization ,• which regards 

 the introduction, or development, of magnesia as subsequent to the de- 

 position of the calcareous matter, and as connected with the proximity 

 of masses containing that earth, and heated to a very high temperature. 



O O 



