1921] on Severn Crossings and Tidal Power 319 



the first instance, and would also afford facilities for the construction 

 of a barrage at a later date. 



A train ferry would not be a really workable proposition until 

 after the construction of the barrage, and then it would probably 

 not be required. 



The great range of tide and the shallowness of the margins of 

 the estuary, together with the speed of the tidal currents, are all 

 points to be taken into account before adopting a train ferry there. 



An entirely new tunnel is not a proposal to be looked upon with 

 favour at the moment. 



The gradients on the Severn Tunnel route are severe, owing to 

 the necessity for tunnelling underneath the deepest part of the 

 Severn, which is known as the " Shoots." The rail level of the 

 Great Western main line is at this place about 130 feet below 

 Ordnauce datum. 



The cost incurred in the construction of the Severn Tunnel and 

 the annual cost of pumping ever since the opening in 1886, as well 

 as the cost of working the steep gradients, have all militated against 

 the driving of another tunnel even for railway purposes. 



There is no satisfactory way of economically accommodating 

 road, rail and pedestrian traffic all together in one tunnel, after the 

 manner of Stephenson's Newcastle High-Level Bridge. This is a 

 great drawback, as it is of first consequence that a new crossing 

 should provide for all kinds of traffic. 



There are also questions of ventilation to be considered in a deep 

 subaqueous tunnel. 



It may, however, be pointed out that the duplication of the 

 up-line on the English side of the estuary — mainly in the open, 

 though partly in tunnel — would at comparatively small cost add 

 considerably to the traffic-carrying capacity of the tunnel. 



We are, however, mainly concerned with the barrage as con- 

 structed in the first instance or at a later date. 



Two considered proposals which have been put forward may now 

 be referred to : — 



1. By Messrs. Addenbrooke, Meik and Twinberrow, who favour 

 a site near Beachley ; and 



2. By the Ministry of Transport, which favours a site near the 

 Severn Tunnel at New Passage. 



These proposals are to some extent on similar lines, modified by 

 local circumstances ; but before dealing with these I wish to express 

 my thanks to Messrs. Addenbrooke, Meik and Twinberrow, and to 

 the Advisers of the Ministry of Transport, for very kindly putting 

 information at my disposal and generally affording me a number of 

 facilities. 



Both proposals involve : — 



1. The construction of a dam across the Severn in order to utilise 

 the valley of the river above the dam site as a reservoir. 



