438 GEOLOGICAL SURVEY OF THE TEREITOEIES. 



I will proceed to describe in detail the various beds composing- the great 

 thickness of strata exposed at and near Coalville ; also to explain their 

 order of succession, the nature of the organic remains found in each, &c. 



In order that these remarks may be the more readily understood, the 

 accompanying section has been prepared, from observations made at 

 the locality during the past summer. It runs from the principal coal- 

 bed near Coalville, in a northwesterly direction to Echo Caiion, a dis- 

 tance, by a right line a little obliquely across the strike of the rocks, of 

 perhaps three to three and a half miles. 



It may be proper to explain here that the beds were not always found 

 well enough exposed to afford absolutely exact measurements of their 

 thickness, while the elevations of the ridges crossed, as well as the 

 breadth of intervening valleys, were merely estimated. Another sec- 

 tion across the same outcrops on a different line, even at no great 

 distance from that of the section here given, would probably not agree 

 in minor details, because the beds are liable to vary in thickness and 

 composition at different localities in this series of rocks. The heavy 

 beds of harder sandstone are more persistent, and, as might be expected, 

 generally more exposed than tljose of softer material. Those of soft, 

 decomposing sandstones, shales, clays, &c., more frequently form slopes, 

 and consequently are more apt to be covered and obscured by loose 

 earth. In some cases we, therefore, had no other means of determining 

 the nature of the strata occupying such spaces, than by examining the 

 disintegrated surface materials, and a few small projecting ledges. 

 Hence some of these spaces that appeared to be occupied by clays or 

 shales, with only a few intercalations of sandstone, may be mainly or 

 entirely made up of soft sandstones, or alternations of the same with 

 clays and shales. Again, it is an. imjDortant point to be remembered, 

 that there may be other beds and seams of coal, in addition to those 

 represented in the section, because these coals generally occur in, or 

 are connected with, clays and shales, or other soft beds such as are most 

 frequently hidden from view. 



A mile or so in a south(Histerly direction from Sprigg's mine, situated 

 directly in Coalville, coal has been found in one or two openings not 

 more than about forty feet above the valley of Weber Biver ; and the 

 bed or beds have been by some supposed to hold a lower position in 

 the series than the main coal (division 5) of our section. The locality 

 of these openings, with relation to the known position and dip of the 

 main bed, would certainly indicate for them a lower horizon in the se- 

 ries, and they may possibly belong lower ; but from all the appearance 

 at these excavations, (which had partly fallen in at the time of our 

 visit,) I have the impression that this coal is merely ;i i)ortion of the 

 same bed thrown out of its natural horizon with relation to the rocks 

 represented in the section, by the same j)owerful forces that upheaved 

 and tilted all of the strata of this region. We did not see more than 

 five or six feet of this coal exposed, but it is overlaid by a sandstone 

 similar to that forming the roof of the main bed at Sprigg's mine in 

 Coalville, and seemed to correspond in other respects, excepting in show- 

 ing a (probably local) reversed dip. 



Between this locality and the lowest beds represented in the section, 

 'as they are seen nearly at Coalville, there is a space not well exposed at 

 any points examined, and consequently we did not determine the thick- 

 ness and nature of the beds occupying the same. 



Commencing, then, with the lowest strata represented in the section 

 on the right, and describing the beds in ascending order, we have the 

 following series : 



