267 



was resorted to in order to prevent leakage, and the engineering 

 seems to have been of a perfect character. At the present day 

 little more could be designed to insure secvu-ity, except, possibly, 

 that concrete would be largely employed in substitution of, Qr 

 in addition to, some of the work. 



There were 24 shafts, 22 of which are now traceable on the 

 ground, and are shewn on the Longitudinal Section, but none 

 of them are now open, and notwithstanding the smoke made by 

 vessels in passing the Tunnel, no difficulty is experienced about 

 its ventilation. Indeed, when one of the shafts (that in the 

 valley where the Great Western Railway crosses over the 

 Tunnel,) fell in some few years ago, I thought of keeping it open 

 permanently, but found that the ventilation was rather injured 

 than improved by its being left open, as it had a decided 

 tendency to interfere with the set of the ventilating current ; 

 and whilst it remained open there were many complaints from 

 boatmen of the Tuixael having got more smoky than it was 

 formerly ; I therefore caused it to be again closed, and such 

 complaints ceased. 



It is unfortunate that in consequence of the closing of the 

 shafts no section of the hill can now be seen, except at the 

 valley shaft, (before referred to, No. 9 from the Coates face on the 

 longitudinal section,) where the slabs covering it may be easily 

 removed and the beds of the Great Oolite, through which it is 

 sunk, seen ; but on the line of the Tunnel itself there can be no 

 doubt whatever about the identity of the strata which have 

 been pierced. Beginning at the west (Sapperton) end, after 

 passing through but little detritus and talus which has tumbled 

 from the face of the hill above, the Fullers Earth is soon 

 reached. (This constitutes the "Marie, Rubble and Loose 

 Rock" before mentioned in reference to Charles Jones' work 

 here.) 



The Fullers Earth was fully exposed on June 25th, 1868, 

 when a portion of the roof of the Tunnel fell in at the point 

 marked on the section, as well as at other times when repairs 

 to the arch or side walls have been executed. At about 580 

 yards from the Sapperton face the Fullers Earth is passed, and 



