94 GILPIN PICTOTJ COAL FIELD. 



the coal seams, occur in so short a distance, I would venture to 

 suggest that they render the theory of the alleged unconformity 

 of the measures lying to the east of the old Mill Road fault of less 

 weight, especially when as in the Geological Survey report, the 

 bend of the measures to the east, and the quick change from shales 

 to sandstones are brought forward in the absence of more definite 

 knowledge, as the signs of an important fault. 



At present we are best acquainted with the western side of the 

 black shales, and the experience of the miners shows that the change 

 from the soft carbonaceous black shales to the post and sandstone 

 rocks is very sudden, and may be marked by a line drawn from the 

 mouth of Coal Brook to the old Colin Pits. On the east side of 

 the East River, the thickness and uniformity of the black shales 

 exposed, almost continuously, from the mouth of McLellan's Brook 

 to the Grant farm, coupled with the large beds of sandstone, sunk 

 through one-third of a mile eastward, would allow on the east side 

 an equal sudden change from carbonaceous to arenaceous measures. 

 Still following the line of synclinal we have next to notice the 

 oil shales opened on McLellan's Brook, one quarter of a mile 

 north of the Fulling Mill. These oil shales are found to occupy 

 the apex of a synclinal with a north-east course, and are considered 

 with every appearance of reason the equivalents of the oil shale 

 opened on the Marsh Brook and also on the property of the Merri- 

 gomish Coal Company, three-fourths of a mile to the north-east of 

 the Marsh pit ; their dip and strike at these points being conformable 

 to the seams of the Marsh group. 



A short distance to the south of the Fulling Mill are a series of 

 faults bringing up lower measures Avhich come abruptly against the 

 seams of the Marsh and McBean's groups. The effect therefore of 

 these faults has been to throw the crops of the oil shales considerably 

 to the north of the position they would naturally occupy at the 

 south-west apex of the McBean synclinal, and to bring into the posi- 

 tion formerly occupied by them the series of coal seams known as the 

 McLean and Mountain groups. We are thus enabled to trace this 

 comparatively shallow synclinal from end to end of the coal field, 

 and to show that its presence has a great effect on the probability of 

 he extent of the Albion or Main seams across the whole district. 



