468 C. T. CLOTTGH ON THE SECTION AT 



It must be understood that the above section refers to the Force 

 itself, the actual place where the water conies over. The sections 

 on either bank of the Tees a few dozen yards below the Force differ 

 from that at the Force itself, and at the same time differ inter se. 



On the north bank, at about 20 yards below the Force, it can be 

 distinctly seen that there is no separate bed c, and that the space 

 between the top of a and the bottom of c is one uniform mass of basalt. 

 We have, then, the following as the section: — 



Basalt, 32 feet (-f any that may be above the level of the top of the 



basalt at the Force). 

 Shale, 12 feet. 

 Limestone, 32 feet. 



We will call this section the section at X. 



On the south bank the section, at a point about 30 yards below 

 tho Force, is: — 



Basalt, 24 feet (+ any that may be above the level of the top of the 



basalt at the Force). 

 Shale, 20 feet. 

 Limestone, 32 feet. 



We will call this section the section at Y. 



Owing to the banks being, in places, inconveniently steep, and 

 bearing a thick covering of hanging trees &c, the entire passage 

 between the above three sections cannot be quite so well seen as one 

 would wish ; enough, however, is shown to enable one to come to a 

 safe conclusion as to the true state of the case. On looking at the 

 section at the Force more carefully, it is distinctly seen that the bed 

 of shale, b, is thicker on the south side than on the north side of the 

 Force — that from 1| foot it dwindles down to one foot, and from one 

 foot it dwindles more and more as we go towards the section at X, 

 until it is only doubtfully represented by a thin line marked by ferns 

 and grass, and that this thin line then ceases, and we get the state 

 of things at X — that, on the other hand, as we go from the Force 

 towards the section at Y, the bed of shale, b, gets thicker and thicker 

 (from 1J foot it gets to 2 feet, and so on), until, at a point about 

 20 yards below the Force, it is 3 feet thick, and in 10 or 12 yards 

 more it has thickened out and formed one mass with the bed of 

 shale, d ; and now there is no underflow of basalt. 



It appears, then, quite safe to conclude that the underflow of 

 basalt, which has its origin from the main mass at X, gradually thins 

 out as we go south-west and south from this point, until at Y it has 

 ceased altogether. 



If we examine the bank a few yards beyond X, we find the sec- 

 tion change again, and again we have an underflow of basalt separ- 

 ated from the main mass by a thin bed of altered shale, thus: — 



Basalt. 



Sandy shale, about 2 feet. 



Basalt. 



The top of the underflow of basalt here is roughly on the same 



