270 



the Railway Company in piercing tlie hill, in such various 

 directions, has been to obtain a perfect and exact knowledge 

 of its stratigraphic condition down to the level at which their 

 lowest heading passed, and to enable Mr. Breketon, the 

 Engineer, to prepare the admirable section accompanying this 

 paper, which he has very kindly allowed me to copy and use 

 for the information of the Cotteswold Club. That section has 

 been reduced to the same scale and referred to the same datum 

 (being that of the Ordnance, viz., mid-tide sea level) as the 

 section of the Canal Tvmnel. The ridge in one case attains 

 an elevation of 613 feet, and in the other of 593 feet above 

 mid-tide sea level, and read together the two sections show 

 the structure of the hill at Sapperton without any speculation 

 or doubt for a depth of 250 feet to 270 feet down from the 

 summit. 



The Drawings which accompany this Paper are as follows : — 



A is a longitudinal section of the Canal Tunnel, on a scale horizontal 

 400 feet, and vertical 40 feet to the inch, prepared from my own 

 -working sections, and is illustrated by the cross sections, viz : 

 No. 1 where the Tunnel is formed in Fullers Earth Clay. 

 No. 2 " " in loose Oolitic Rock. 



No. 3 " " in ordinary Eocking. 



No. 4 where Trunk Forming was used in consequence of 

 springs entering in at, or towards, the bottom of 

 the Tunnel, with longitudinal section and plan 

 referring to same. 

 All these cross sections are on a scale of 8 feet to the inch. 



B is a longitudinal section of the Great Western Eailway Tunnels, 

 prepared from working sections of the Engineer, (Mr. E. P. Brereton, 

 Mem. Inst. C. E.) on scale 400 feet horizontal, and 40 feet vertical to 

 the inch. 



No. 5 is the general cross section to same, on a scale of 

 8 feet to the inch. 



C is a General Plan, on a scale of 20 chains to the inch, showing the 

 exact positions of the two Tunnels at Sapperton. 



