EMPIEE HILL. 177 



Along the steeper Avestern face of this shoulder the Cambrian and Silurian 

 outcrops rest on the Archean, and the top of the shoulder is at the contact 

 of the Blue Limestone and overlying White Porphyry, which has been 

 quite extensively prospected, without, however, disclosing any considerable 

 ore bodies. 



At the head of the north branch of Weston's gulch the ridge which sep- 

 arates it from Empire gulch presents a steep slope to the southward, which 

 affords a good section of a series of limestones, shales, and sandstones in a 

 thickness of from 300 to 600 feet, belonging to the Upper Coal Measures, 

 from which the following fossils were obtained: 



Arckceoccidaris, sp. undet. 

 Polypora, sp. undet. 

 FenesteUaperelegans. 

 Synocladia, sp. mulct. 

 Rhombopora lepidodendroides. 

 Palceschara, sp. undet. 

 Streptorynchus crassus. 

 Chonetcs granulifera. 

 Productus costatus. 



Macrocheilus ventricosus. 

 Phillipsia, sp. uudet. 

 Productus Nebrascenais. 

 Chonetes glabra. 

 Spirifera Rocky montana. 

 Athyris subtilita. 

 Productus Prattenanus. 

 Nucula, sp. undet. 

 Astartella, sp. undet. 



Section F, Atlas Sheet IX, which passes through the ridge, shows the 

 structural conditions which prevail here. Where these beds join the fault 

 they stand quite vertical and give evidence of having been subjected to great 

 pressure, as shown in the specimen represented in Fig. 2, Plate V (page GO) ; 

 but at a little distancefrom the fault it can be seen that near the top of the ridge 

 they gradually bend over to the westward, until a few hundred yards west 

 they assume the normal dip of 20 to the eastward. Below these, both on 

 the ridge and in geological succession, are the sandstones of the Weber Grits, 

 which form the mass of a low rounded hill. Along the western face of this 

 hill, and immediately above the White Porphyry, is a considerable thick- 

 ness of compact black argillaceous shale, impregnated with pyrites. This 

 black shale has been opened in several places by prospect holes, and from 

 it were obtained numerous casts of fossils, in which the calcareous matter 

 of the original shell has been entirely replaced by very minute crystals 

 of iron pyrites, so minute that the form of the shell is still distinctly 

 visible in those which are newly opened, though they rapidly decompose on 



MON XII 12 



