EASTERN FOOT-HILLS. 35 



In the more compact and massive sandstones, transverse bedding forms 

 a very prominent and marked feature of the Triassic Red Beds. 



In addition to the well-defined limestone beds, many of the horizons in 

 the upper impure sandstones appear highly calcareous, which is, however, 

 not evident to the eye, but which, when they are treated with dilute acids, is 

 indicated by a brisk effervescence. A typical specimen of the red sandstone 

 in our collection, taken from near the entrance to the Big Thompson Canon, 

 and not far below the top of the Triassic series, presents a fine-grained fria- 

 ble texture, a deep red color, with a shaly, laminated structure. A fragment 

 from this rock was subjected to chemical analysis by Mr. B. E. Brewster, 

 with the following result : 



Ferric oxide 1 .30 



Alumina 2.15 



Lime 6.07 



Magnesia - 4.40 



Potassa - - : 2.38 



Soda 1.14 



Carbonic acid 9.00 



Water 1.62 



Silica 67.37 



Alumina 5.69 



101.12 



Insoluble residue 



This analysis shows the presence of a large amount of soluble carbon^^ 

 ates, including a high percentage of dolomite, and a considerable admixture 

 of argillaceous materials. So large a proportion of carbonate, with no trace 

 of gypsum, occurring in a formation in which many of the horizons are 

 marked by the presence of heavy deposits of the latter salt, is not mthout 

 considerable interest. 



Underlying the shaly sandstone a short distance, occurs a deep red bed, 

 somewhat coarser-grained, still more friable, and without any laminated 

 structure, which, upon being treated with acid, gave no indication of the 

 presence of soluble carbonates. Laminated impure shales, from a well- 



