1882.] on the Malcing and WorJcing of a Channel Tunnel. 139 



locomotives are used, drawing a train behind them, and such cars as 

 these make the outward and homeward journey, or 7f miles in all, 

 without requiring any replenishment with air. No doubt the reservoirs, 

 to contain a sufficient store of air to propel the train through the whole 

 length of the tunnel, would be heavy, but they would be but little, if 

 at all, heavier than the weight of the tender with its load of water 

 and coals, added to the weight of the boiler with its charge of water, 

 both of which are needed in the working of an ordinary locomotive, 

 but are not wanted when compressed air engines are used. But 

 there is, however, no occasion whatever to carry the whole charge of 

 air needed for the entire journey through the tunnel ; there will 

 remain in the completed tunnel the air-pipe that was laid down to 

 drive the perforating machinery. This air-pipe can be always kept 

 charged with air. Valves will be provided at frequent intervals, and 

 thus it will be perfectly possible to re-charge the reservoirs, habitually 

 at an intermediate station, or indeed anywhere (say within an eighth 

 of a mile) on the line, should such re-charging from any accidental 

 cause be needed. The great advantage of compressed-air propulsion, 

 under such circumstances as those which prevail in a tunnel 20 

 miles long, is that every train which goes through, instead of using 

 and vitiating the air, is in its very progression the cause of thorough 

 and efficient ventilation. 



As I have said, working by compressed air is no longer an experi- 

 ment. It is a mode of propulsion that has been in successful daily 

 use for several years in France ; and I trust that before many months 

 are over it will be seen in equally successful daily use in London, and, 

 subject to the development of electrical propulsion, and subject to the 

 great temptation to use the ordinary locomotive, it appears to me, 

 as I have said, that compressed air is that one of all the modes by 

 which a train can be moved which commends itself to one's judgment 

 as the system to be employed for the working of a Channel tunnel. 



If this lecture has been found more than usually tedious, I must 

 ask you to attribute it to the fact that I have endeavoured to 

 deal with the subject in an entirely abstract manner, and so 

 as to avoid contentious questions of any kind. I set out with 

 that firm determination, and I trust I have not swerved from it, but 

 I do not like to conclude without saying a word on the means 

 by which the advent through the tunnel of undesirable persons 

 may be prevented, and I will illustrate my meaning by showing how 

 a hitherto unsuggested source of danger might be met, and as this 

 source has as yet not been suggested, it is clear no contention can 

 have arisen on the subject, and I cannot therefore be accused of 

 dealing with contentious matter. This danger I will call smuggling ! 

 and I will ask you to let me describe a plan by which it appears to 

 me that smuggling of any kind could be rendered very difficult, and 

 whereby a custom-house officer could have ample time, and perfect 

 security, to examine the luggage of the passengers, or to (it may be) 

 inquire into the morale of the passengers themselves. 



