884 report -1884. 



and inventions, I should set myself a task -which could not have heen fulfilled had 

 I devoted the whole of the time I had at my command to the purpose. I had, 

 indeed, thought of making his work the subject of my address, but I felt that his 

 loss was so recent, that I could not trust myself to attempt it. There is no need 

 for me to dwell further upon this most painful topic. He was known to you all, 

 he was honoured and loved by you all, and by every member of this Association 

 he had so faithfully served, and over which he had so ably presided ; and he enjoyed 

 the respect and esteem of the best intelligence of England, the land of his adoption ; 

 of the Continent, his birthplace ; and of Canada, and of the United States, whose 

 populations are always ready to appreciate scientific talent and the resulting in- 

 dustrial progress. It is not too much to say that few more gifted men have ever 

 lived, and that with all his ability and talent he combined a simplicity, a modesty, 

 and an affectionate disposition that endeared him to all. 



I am sorry to conclude my address to you in this mournful strain. I have 

 endeavoured to confine my allusions to our dear friend within the narrowest 

 limits, but if I have overstepped these I trust you will forgive me, remembering 

 that ' out of the fulness of the heart the mouth speaketh.' 



The following Papers were read : — 



1. The Forth Bridge. By Benjamin Baker, M.Inst.C.E. 



2. The Severn Tunnel Railway. By J. Clarke Hawkshaw, M.Inst.C.E. 



This paper described the Severn Tunnel Railway works, begun in 1873, and 

 now approaching completion. The railway is being made to shorten the direct 

 railway route between the South of England and South "Wales. It passes under 

 the River Severn about half a mile below the present steam ferry, which connects 

 the South Wales and Bristol and New Passage lines. The river, or estuary, is 

 about 2\ miles wide. The length of the line is 7h miles, of which 4j miles is 

 in the tunnel which passes under the Severn. The bed of the river i9 formed 

 principally of Trias rocks (marls, sandstones, and conglomerates), in nearly hori- 

 zontal strata. These overlie highly inclined coal measure shales and sandstones, 

 which are also exposed in the river bed. The tunnel is made almost wholly in 

 rocks of the Trias and Coal-measure formation, the exception being a little gravel 

 passed through near the English end. 



The lowest part of the line is below the shoots, the deepest part of the river, where 

 there is a depth of 60 feet of water at the time of low water, and 100 feet at the time 

 of high water. Below the shoots the line is level for 18 chains, rising 1 in 100 to the 

 English end, and 1 in 90 to the Welsh end. Below the shoots there is a thickness 

 of 45 feet of rock (Pennant sandstone) over the brickwork of the tunnel. Under 

 the Salmon Pool there is less cover, only 30 feet of Trias marl. Much water has 

 been met with throughout the works, which have been flooded on several occasions. 

 In 1879, the works under the Severn were drowned for some months by the 

 eruption of a large land spring into one of the driftways under land on the Welsh 

 side of the river. On another occasion, a cavity was formed from the driftway 

 under the Salmon Pool to the bed of the river, when a hole, 10 feet by 10 feet, was 

 found in the marl. The works were flooded by the water which found an entry 

 through this hole. It was filled with clay, and the tunnel is now finished 

 beneath it. 



The quantity of water now being pumped is about 19,000 gallons per minute. 

 Additional pumps have been erected, as the large land spring, which has been 

 penned back by a brick wall, still remains to be dealt with. When all the pumps 

 are available, the total power will be equal to 41,000 gallons a minute. 



The tunnel is for a double line of way, and will be lined throughout with 

 vitrified bricks set in Portland cement mortar. 



It is being made by the Great Western Railway Company. Sir John Hawk- 

 shaw is engineer in chief; Mr. C. Richardson, engineer; and Mr. T. A. Walker, 

 the contractor. 



