56 



Main Coal with Shaley Coal, do. 8 



Strap 3 



Perrink ,., ... ... ... 3 6 



White Axen ... 3 



Eed ditto 3 



Wilmot's Vein 1 6 



Total ... 28 



The next formation to which I would call your attention 

 (and that very briefly) is the 



MILLSTONE GRIT. 



In the northern end of the basin its thickness has been 

 estimated at 950 feet ; but 1 am disposed to think that in 

 the southern end of the coal-field it is much less. Mr. 

 Saunders appears to have mapped its outcrop very carefully 

 between Coleford and Nettlebridge, and taking the average of 

 that outcrop in connection with the average of inclination, I 

 arrive at the conclusion that it cannot exceed 500 feet. It 

 would appear to be wanting altogether at one point in the 

 neighbourhood of Ashwick, but that is exceptional ; and in 

 the absence of direct evidence, I have shown it in its legitimate 

 position in the section from Chewton to Combe Down takino- 

 the outcrop between Coleford and Nettlebridge as the safest 

 guide to its thickness. 



We now come to the lowest member of the carboniferous 

 strata, viz., 



THE MOUNTAIN LIMESTONE, 



With its accompanying shales. Much remains to be done in 

 working out the individual beds of this formation in the 

 southern part of the district, but I will at present only 

 attempt to define its total thickness. I have been rather at 

 a loss to account for the low estimates which at different 



i 



