cclvi GENERAL SUMMARY OF SCIENTIFIC AND 



the lower bed of homogeneous chalk, this stratum being 

 500 feet deep on each shore from high-water mark. In es- 

 tablishing the basis for this opinion, an examination was 

 made across the Channel by dropping, from a steamer, a 

 weighted instrument in 500 places, the apparatus running 

 with great velocity to the bottom, and bringing up chalk 

 where it was expected. The current is so strong along 

 the proposed line that the bottom is washed quite clean, 

 as the experiments conducted showed the absence of any 

 deposit. From the examinations made there is every rea- 

 son to believe that the chalk is continuous, and that it 

 stretches beneath the sea uninterruptedly across the Chan- 

 nel. The maximum depth of water on the line of the pro- 

 posed tunnel nowhere exceeds 180 feet below high-water 

 mark, being deepest in the centre, and gradually diminish- 

 ing in depth toward the sides. The tunnel itself would be 

 placed by the engineers at such a depth that the thickness 

 of the rock-bed over it w T ould be nowhere less than 200 feet ; 

 and this depth, which is ample for security, would permit 

 the railway approaches to be formed with tolerably easy 

 gradients. The danger to be apprehended from the possi- 

 ble existence of fissures in the chalk, and consequent infil- 

 tration, is answered by referring to the experience had dur- 

 ing the construction of the Brighton Tunnel, through the 

 comparatively incompact upper chalk, for a distance of five 

 and a quarter miles along the sea-shore, and from twelve 

 to twenty feet below high-water mark, in close proximity 

 to the margin of the sea. In this instance, although con- 

 siderable water, mainly fresh, was met with, the work of con- 

 struction was not notably obstructed in consequence. The 

 engineers, finally, are unanimously of the opinion that the 

 problem of ventilating the tunnel is easy of solution. 



The future disposition of this magnificent scheme will 

 probably be that the preliminary work (involving perhaps 

 the cutting of galleries from both sides some distance un- 

 der the sea) will be continued by private enterprise, until 

 the feasibility of the undertaking is either disproved or es- 

 tablished beyond cavil. Should this last prove to be the 

 case, as seems quite probable, the two governments interest- 

 ed will doubtless be asked to come to the aid of the enter- 

 prise by the grant of a liberal subsidy. 



