1881.] ^*i [Stevenson. 



river at Pennington's mill and is well exposed immediately below the dam. 

 It is light gray, cross-bedded and contains many rude impressions of plant 

 stems. Some of its finer layers yield a good firestone ; and the lining of 

 Pennington's forge, constructed of this sandstone, has stood for three years. 

 This is said to bear a dash of cold water without cracking, even when at a 

 bright red heat. The little Coal bed. No. 11, is of no value, but the clay 

 underneath it makes excellent brick though it is too ferruginous to be 

 used for firebrick. No. 13 is shown immediately below the forge and 

 some of its layers do Avell as firestone. Much coarse conglomerate occurs 

 in Nos. 14 and 17, and there are several coarse layers in No. 24. Many 

 impressions of plant stems were seen in No. 32. 



The Goal beds, Nos. 16, 18 and 20, are no longer exposed in the gap. 

 They were opened by Mr. Pennington, but proved worthless. No. 16 was 

 opened both in the bank of the stream and on the hillside ; it is 5 feet thick 

 at both places, but the coal and shale are in nearly equal proportion and 

 are so mixed that the bed is without value. A bed, shown on the ridge at 

 about two and one-half miles from gap, is supposed by Mr. Pennington to 

 be the same with No. 16. It is 2 feet 9 inches thick and yields good coal, of 

 which some has been hauled to Jonesville. 



The other beds consist only of a worthless commingling of coal and shale. 

 No. 23 may have been a Goal bed at one time, but if so, it was torn up and 

 re-distributed during the formation of the overlying sandstone, for now it 

 consists of simply small pockets of pulverized coal scattered through 

 7 feet of sandstone. 



The massive beds of this group project above the surface like dikes and 

 some of them overhang the river. 



The Lower Carboniferous limestone is well exposed at many places along 

 Stone mountain, but continuous exposures were found only in Penning- 

 ton's gap, where the following succession was made out, the thicknesses 

 being estimated : 



Mountain Limestone Group. 



1. Imperfectly exposed 40' 



2. Sandstone 15' 



3. Dark fissile shale 5' 



4. Sandstone 20' 



5. Imperfectly exposed, much shale 200' 



6. Sandstone 75' 



7. Shale with thin limestone 35' 



8. Sandstone 40' 



9. Concealed 60' 



10. Calcareous sandstone 120' 



11. Dark fissile shale 5' 



12. Calcareous shale 90' 



13. Argillaceous limestone, fossiliferous 15' 



14. Imperfectly exposed 60' 



15. Massive limestone '. 25' 



16. Calcareous shale, fossiliferous 50' 



