TRANSACTIONS OF SECTION G. 871 



* Elephant and Castle ' ; and by an Act of the present year the company has been 

 invested with power to extend the line to the Clapham Road at Stockwell. The 

 subway is intended to give better access to and from the City for the densely 

 popvdated and rapidly gi-owLng districts on the south side of the Thames, now only 

 directly served by omnibuses traversing crowded thoroughfares, including LondoH 

 Bridge. 



Rather over three miles in length, the ' up ' and ' down ' lines will be carried in 

 separate tunnels placed at such a depth under the surface of the roads as to avoid 

 all interference with sewers and pipes. Where not under the river the subway 

 will be under the roads entirely. At each station, of which there will be six, 

 powerful hydraulic lifts will be provided in addition to the stairs. 



The traction will be by stationary engines and endless cables, similar to the 

 system adopted on cable tramways. By this means light trains can be economi- 

 cally run at short intervals in place of the heavy locomotive trains now run on the 

 underground railways. 



The whole power, both for traction and lifts, will be placed at one station about 

 the middle of the line. 



The carriages, which will be very commodious, are to be of the longitudinal 

 type, similar to Pullman and ordinary tramway cars. 



The first tunnel was commenced on the north side of the Thames in November 

 last year. By the beginning of September it had been driven under the river 

 Thames and the roads for a distance of 1,600 feet. The second tunnel, commenced 

 at a later date, was progressing at the same rate. The mode of construction is very 

 simple. An overlapping ' shield " at the advanced end of the tunnel, forced for- 

 ward by hydraulic pressure as the material is excavated from before it, enables six 

 rings of cast iron, each 1 foot 7 inches long, to be built up under cover of the over- 

 lapping cyhnder every day. As the shield is advanced an annular space is left 

 outside the iron tunnel lining, and this is fiUed with semi-fluid cement by means of 

 an apparatus worked by compressed air, which is fully described in the paper. 

 Arrangements for tunnelling through soft or loose water-bearing material were also 

 described, with illustrations and a model. 



3. Oti a High-speed Steam or Hydraulic Revolvimj Engine.^ 

 By Arthur Rigg. 



The author describes results of further experience with a new description of 

 revolving engine, of which a general account was given at the meeting of the 

 Association last year. 



The engine consists of several cylinders, all of which revolve on a coimnon 

 centre, while their pistons are connected with crank-pins on the rim of a wheel 

 which turns on a different centre. By this arrangement there is obtained a move- 

 ment of the pistons within the cylinders, corresponding in effect with a true 

 reciprocation ; and as all the pistons and cylinders are balanced with each other, 

 there is no loss of power or excessive vibration such as is found to accompany 

 ordinary reciprocation ; and engines of this revolving type can be driven at very 

 high speeds with a perfectly steady and miiform motion. 



One hj'draulic engine of this class has been running for some months in London, 

 driving a dynamo and 100 incandescent lights from the pressure mains of the 

 Hydraulic Power Supply Co. The pressure is 700 lbs. per square inch, and this 

 particular engine makes 2-50 revolutions per minute, developing 1-3 horse-power, 

 with 33 gallons of water per minute ; this corresponds with a duty of 80 per cent. 



It is governed by causing the piston-stroke to vary ; and this method of re- 

 gulation maintains a uniform speed, although the power may vary, so that the 

 lights remain quite steady, however many be switched on or off. 



A similar engine has been diiving a capstan at the Mill wall Docks, London. It 

 can be reversed or give any variation of power in either direction of motion. 



' Published in eaienso in Iron, Sept. 9, 1887. 



