138 Sir Frederick Bramwell [May 19, 



an electric railway between Charing Cross and the Waterloo Station ; 

 and it is therefore by no means improbable that by the (I trust) very 

 few years within which the Channel tunnel will be ready for the 

 reception and working of its trains, electric j)ropulsion may have 

 been so far developed as to render its employment in that tunnel 

 judicious. 



The next system I adverted to was the pneumatic, that wherein a 

 train is driven along by a very slight differential air-pressure exerted 

 over the area of a piston loosely fitting the tunnel. This mode of pro- 

 pulsion is one that ensures the most ample ventilation, in fact not 

 merely ample but even unnecessary, that it is to say, it involves the 

 changing of the whole of the air in the tunnel at the passage of every 

 train. It will be found, however, that although admirable for 

 working the traffic of a subterranean Metropolitan line with stations 

 at frequent intervals and with very numerous trains, it would not be 

 a very economical mode of working trains through a tunnel 20 miles 

 long ; the skin resistance to the passage of the air even at moderate 

 velocities being so great as to involve the consumption of a large 

 amount of horse -power. 



The last of the modes of propulsion that I enumerated, is that 

 wherein there is the employment of com2)ressed air, and, setting 

 aside the electrical mode which, as I have said, may, by the time the 

 tunnel is ready for traffic, be so far developed as to be the most 

 advantageous of all, compressed air is the one that commends itself 

 most to my mind. This system of propulsion is now by no means an 

 experiment. In carrying it out, as probably you are aware, there are 

 employed in the train reservoirs of air compressed to any desired 

 extent by means of compressing engines, and this air, on being 

 allowed to escape from these reservoirs through engines practically 

 of the nature of the ordinary steam engines, drives them, and by 

 them draws the train. 



Several modes of employing compressed air have been proposed 

 and have been put to work, among others one by Colonel Beaumont, 

 but the mode with which I am best acquainted, and about which there- 

 fore I am the most comj^etent to speak to you, is that which has been 

 in practical work every day for now nearly three years at Nantes. In 

 that town there is a service of tramcars starting every ten minutes 

 from each end of the line, which is 3| miles long, and traversing the 

 very heart of the town and the busiest part of it, running for a 

 considerable distance along the quay, which is one of the leading 

 business thoroughfares. 



In this system the air is compressed to only 30 atmospheres, and 

 is allowed to escape by ingenious, but simjile, means at regulated 

 pressures to drive the engine, but prior to passing into the engine it 

 is heated by traversing a vessel containing hot water and steam under 

 pressure, which are charged into the vessel before leaving the depot. 

 The bulk of the cars employed contain their own reservoirs and their 

 own engines, but on holidays, and on busy days, cars in the nature of 



