﻿1861.] 



HECTOR ROCKY MOUNTAINS, ETC. 



423 



rate. At the Rocky Mountain House, in latitude 52° 21' N., longi- 

 tude 115° 10' W., where I had the best opportunity of examining this 

 formation, I divided it into three groups, judging from the mineral 

 composition alone ; as they were found to pass from one to the other 

 without superposition, just as we might expect to find in a shallow 

 lagoon-deposit. 



1st. Coarse-grained sandstone, composed of angular grains of 

 quartz cemented by calcareous matter, present in small quantity. 

 This sandstone forms bold perpendicular cliffs, often 150 feet in height, 

 and hemming in the river on both sides. It resembles the descrip- 

 tions given of the sandstone of the " ramparts" on the Mackenzie and 

 Peace Rivers ; and indeed on all the rivers this formation may be 

 traced by this marked feature as far south as the Missouri at least, as 

 a drawing of the falls on that river (given in Pac. Rail. Rep.) exactly 

 resembles these sandstone cliffs. 



The 2nd group consists of beds of green argillaceous sandstone, 

 which, as it weathers easily, always gives rise to sloping banks, 

 from which protrude concretionary masses. These beds are gene- 

 rally horizontal, but sometimes present a rapid dip towards the 

 edges of basins in the last group in which they seem to have been 

 deposited. They are, however, often overlain by the hard-bedded 

 sandstone. 



The 3rd group more resembles in its mineral characters than the 

 other two the beds at Edmonton, consisting of alternations of clay- 

 shale and argillaceous sandstone in irregular beds, and including 

 deposits of coal or lignite. The shales, which are often very hard and 

 compact, contain fragments of the Yew-like frond, and also stems of 

 plants like sedges. 



Fig. 7 (p. 424) is an attempt to combine the different sections that 

 were observed at the Mountain Fort. The irregularity in the mineral 

 composition is well shown about five miles above that place, where in a 

 very short distance beds of clay and soft green sandstone are suddenly 

 replaced by cliffs of grey and yellow sandstone with heavy bedding*. 



* The features of the strata at the Mountain House are very similar to the 

 description given of the Lower Cretaceous groups at Seargent's Bluff on the Mis- 

 souri by Meek and Hayden, where the following section is described : — 



" 1. Dark-coloured clay with sandstone seams 6 feet. 



2. Light-yellow clay passing into grey sandstone .... 5 „ 



3. Dark clay with fragments of carbonized wood . . . . 1£ ,, 



4. Grey indurated clay or marl with wood 4 ,, 



5. Dark seam like No. 3 8 inches. 



6. Clay like No. 4 3 feet. 



7. Grey sandstone (carbonized wood) 2 „ 



8. Very dark-grey clay, sometimes black, with organic matter 



in the lower part, and crystals of selenite 10 ,, 



9. Grey clay, carbonized wood and hard concretions ... 30 „ 

 10. Grey sandstone with wood 2 „ 



11. Grey clay, with wedge-shaped masses of hard bituminous 

 lignite or coal and round lumps of sulphuret of iron, 

 to the river-level" 



It is mentioned that the beds thin out in many directions, and that some in- 

 crease to a great thickness in a few hundred yards. 



(Mexican Boundary Eep. vol. i. p. 136.) 



