46 



of the surface made by myself, the position of the veins has 

 been ascertained by pits, borings, or by underground level- 

 lings ; and as the section embodies the results of every 

 exploration up to the present time, it is probably as near an 

 approximation to the truth as can be made until the district 

 has been more fully developed. 



I purpose taking the strata in their descending order, and 

 I would call your attention first of all to the 



OVERLYING FORMATIONS. 



These, strictly speaking, form no part of the subject of this 

 paper, but it has been necessary for completeness to show 

 them in the section, and I will, in passing, briefly notice 

 them. The scale being too small to admit of more minute 

 sub -division, I have adopted as nearly as possible the 

 arrangement of Mr. Saunders's geological map. 



Commencing at the eastern end of the section and pro- 

 ceeding westward, we find the leading di-vdsions of secondary 

 strata appearing at the surface in steadily descending order — 

 at the top the Bath oolite, then the fuller's earth rock and 

 fuller's earth, the inferior oolite, the lias, and lastly the new 

 red sandstone, with its associated conglomerate. With regard 

 to the upper four of these divisions there is nothing which, 

 in a paper of this kind, need call for special remark ; but in 

 working out the thickness of the liassic strata for the purpose 

 of this section, 1 was struck with the great increase in their 

 thickness in proceeding eastward. 



While at Paulton the total thickness of liassic strata is 

 only 160 feet, at Dunkerton, where a boring was formerly 

 put down, their thickness was proved to be 198 feet ; and in 

 the trial pit sunk at Batheaston many years ago (for par- 

 ticulars of which I am indebted to Mr. Moore), their tliickness 

 is said to have been 277 feet. Mr. Moore informs me that 

 this increase in thickness is owing to the presence in the 



