ISSi.] on London (below bridge) North and South Communication. 491 



pressed to such a point as to entirely, or partially, balance the pressm*e 

 of the water, in the soil through which the work was being carried 

 out, and thus to stop, or to greatly diminish, its influx. Lord 

 Cochrane showed the means of doing this — of passing men in and 

 out of the work, by air locks — of passing materials in and out by 

 the same means, or by tubes having their ends open but sealed by a 

 column of water ; in fact, he described all that has ever since been 

 found necessary, or even desirable, in compressed-air cylinder sinking ; 

 but, so far as I know, no use was made of the invention until 1850, 

 when it was employed in sinking the cylinders for Rochester Bridge. 

 I felt I ought not to let this admirable invention, of so very remark- 

 able a man, pass without a brief notice. 



The only other executed work, making communication from side 

 to side of the river, below bridge, is that ali-eady referred to — the small 

 subway from Tower Hill. This consists of a cast-iron tube, about 

 7 feet external diameter, and about 6 feet 6 inches clear internal 

 diameter. The engineer was Mr. P. W. Barlow. It was opened 

 for traffic in the beginning of the year 1871, the work being executed 

 in stiff clay the whole way, no difficulties of importance were met with. 

 The authorised capital is 26,000/. It was originally intended to 

 use some mechanical means of transport, but this idea was given up. 

 The toll is a halfpenny, and the persons using it are said to number 

 1,000,000 per annum, or an average of about 3000 per day : a very fair 

 piece of evidence, in favoui' of the needs of increased communication. 

 In the year 1877, a steam ferry for vehicular pui'poses was established, 

 just over the Thames Tunnel, and was opened on the 31st October of 

 that year. The rise and fall of tide were allowed for by counterbalanced 

 platforms, raised and lowered by means of chains, connected to hori- 

 zontal hydraulic presses. This ferry worked for a short time, but a 

 ship ran into the framework of the platform of the Sui'rey side, and 

 shattered it, and for some time past the ferry has ceased to be used. 



With respect to projects : a suggestion that has been made on 

 more than one occasion is to consti'uct a duplex bridge. This is a 

 renewal of a very old plan proposed as far back as the beginning of 

 the century by Colonel Bentham and also by Mr. Dance, the architect, 

 whose bridge, however, was practically a double one. Each of these 

 gentlemen intended his bridge as a substitute for old London Bridge, 

 and proposed to construct it in this manner to allow seagoing vessels 

 to come up the river as far as Blackfriars. 



The diagrams on the walls are enlarged from the drawings in the 

 Eeport of a Parliamentary Committee on this subject, which sat, off and 

 on, for about five years, at the end of the last century, and at the 

 beginning of the present. The intention was to have the bridge 

 double for a short distance, in one case, and for its whole length in 

 the other ; the distance between the two sections being sufficient to 

 accommodate a vessel, so that if it were coming up stream it should 

 pass by an opening in the eastern section of the bridge, the road 

 traffic on that section being stopped, and then the traffic on the other 



