Vol. 68.] CAEBOXIEEEOUS LIMESTONE AT TJPPEK VOBSTER. 61 



On this evidence it would appear to be established that Coal 

 Measures have been proved for a considerable distance under the 

 eastern part of the Upper Yobster inlier, and at no great depth 

 from the surface. 



Other statements by Mr. McMurtrie, also pointing to the con- 

 clusion that the Carboniferous Limestone of Upper Yobster is no 

 more than a superficial mass, are of interest. Referring to the 

 southern margin of the western portion of the inlier, this author 

 writes : — 



' In a garden, behind some cottages at Upjaer Yobster, marked A on plan, 

 a well was snnk many years ago by Mr, Richard Edgell, a bailiff at the Vobster 

 Colliery. It began in Mountain Limestone, but at a depth of 22 feet from the 

 surface it passed into Coal Measures, in which it was continued 4 feet, making 

 a total depth of 26 feet. This information I have obtained from Mr. Edgell 

 himself, who is prepared to vouch for its accuracy, and who has also com- 

 municated another important fact. At the time the well in question was sunk,, 

 tlie workmen at Upper Vobster Quarry [Yobster Old Quarry] having followed 

 the Limestone a little deeper than usual, at a point marked B, passed through 

 it into shale, and it was ascertained, by levelling the ground, tliat the shale at 

 the bottom of the well A was on a level with the shale met with at the bottom 

 of the quarry.' {Loc. supra cit.) 



III. Essential Steuctuee op the Inliee. 



The inlier comprises three portions, namely, two masses of 

 Carboniferous Limestone separated by a band of grits and shales 

 which is faulted in between them. These may be termed respec- 

 tively : (1) The Northern Limestone Mass, (2) the Southern 

 Limestone Mass, and (3) the Grit-&-Shale Mass. 



Many years ago, quarrying operations were confined to the 

 limestones of the Southern Mass. A long quarry running east 

 and west (Yobster Old Quarry) was gradually extended northwards 

 in the Carboniferous Limestone of the Southern Mass, until the 

 Grit-&-Shale Mass was encountered. This quarry was then aban- 

 doned, and a tunnel was driven northwards through the Grit-&- 

 Shale Mass until the Northern Limestone Mass was reached, when 

 quarrying was resumed. A huge quarry (Yobster Quarry) ha& 

 since been excavated in the Northern Limestone Mass, and is still 

 being actively worked. The structure of the inlier has thus been 

 exposed to a remarkable degree. 



The characters of the rocks, and other features of the chief 

 sections, will be described in some detail below. For the sake of 

 clearness, however, a summary of the main conclusions arrived 

 at may be given here, as follows. 



General Conclusions. 



(1) The Upper Yobster Inlier is apparently a lenticular mass of 

 Carboniferous Limestone, and Grits and Shales, superimposed 

 upon overfokled Coal Measures by thrust-movements. 



