94 The Tunnel under the Thames at Blackmail. [March 6, 



of about 1300Z. per yard, while that at Blackwall averages 550Z. per 

 yard. This is most gratifying after the gloomy forebodings by 

 which we were met before we commenced the work. It was at that 

 time predicted, and I was personally warned by members of my own 

 profession, that if we succeeded at all, it would only be by chance, 

 and at the cost of much suffering and death. The success that has 

 attended us is due to all who have been engaged upon the work, and 

 particularly to the skill and untiring energy of three gentlemen, 

 the two resident engineers, Messrs. Hay and Fitzmaurice, and to 

 Mr. Moir, who acts as engineer for, and representative of the con- 

 tractors, Messrs. Pearson and Son. But in claiming for ourselves at 

 the present time credit for the success that has attended our efforts, 

 we must not forget the honour due to those who have preceded us. 

 No one can in a large and complicated modern work such as I 

 have been describing, claim for himself the exclusive credit for the 

 whole or any important part of it. We have been using a shield, 

 under compressed air, jDUshed forward by hydraulic power, and at 

 once the names of Bramah, Brunei and Dundonald remind us that 

 we are largely indebted to them. Much has been said and written 

 about the shield we have used, and some names have been associated 

 with its design. I wish it clearly to be understood that no one has 

 any right to do so, as it is a combination of all the good points in 

 many previous efforts in the same direction. But if to any one is due 

 more credit than to another it is to that remarkable genius the elder 

 Brunei, who, although he was himself unable to use his own invention, 

 saw clearly how the work could be best accomplished, and as far back 

 as 1818 took out a patent for a shield and mode of constructing 

 subaqueous tunnels. As described in and shown on the drawings 

 attached to his specification of 1818, we find a cylindrical wrought- 

 iron shield, divided into working cells or pockets, the tail of which 

 overlapped a tunnel some 20 feet in diameter, which tunnel was 

 formed of cast-iron rings, and the whole shield was to be ju'essed 

 forward by hydraulic jacks. From Dundonald's specification of 1830 

 we get the mode of making a tunnel under compressed air ; and to 

 Bramah is due, in a great measure, the invention of the hydraulic 

 press. Therefore in this as in so many other of our works, it is 

 seen that we owe a deep debt of gratitude to our predecessors for the 

 success we have attained. 



[A. E. B.] 



