1869.] Tlie Projected Merseij Tunnel and Railway. 181 



arises from the disposition which undoubtedly exists to form an 

 unfair comparison between such works and the Thames Tunnel, 

 which, as every one conversant with the circumstances connected 

 with it will know, cost a very large sum, although passing under 

 a river of no considerable breadth. This, however, is no fair 

 criterion upon which to judge of any other case. This tunnel 

 was constructed some forty years suice, when the science of tunnel- 

 making was but little understood, and when it had to be applied 

 upon a very limited scale, without the advantages arising from 

 many later improvements, and without the extensive experience 

 derived during the last forty years from works of this nature, 

 requu-ed in the development of the railway system all over the 

 world. 



This makes a comparison deceptive, to say nothing of the 

 Thames Tunnel having to be constructed under all the difficulties 

 of passing, not through London clay, which it would have done had 

 it been placed a few feet deeper, but through the treacherous and 

 loose silt and gravel of the bed of the river Thames, while the 

 tunnel which forms the subject of this paper will pass through 

 sohd rock. 



To attempt to draw a comparison between this project and the 

 Thames Tunnel is but to show an entire want of acquaintance with 

 the relative circumstances of the two case?, for it must be borne in 

 mind that the Act authorizing the construction of the latter received 

 the Koyal Assent on June 21th, 1824, more than forty-four years 

 since, and that the tunnel was not opened for passenger traffic tdl 

 March 25th, 1843, having occuj)ied a period of eighteen years and 

 three-quarters in arriving at completion. 



Were this work now taken in hand by an Engineer possessing 

 the experience obtained in constructing tunnels since the period 

 above referred to, taking care to place his work deep enough to let 

 it pierce only the London clay (to have done which the present 

 tunnel ought to be fifteen feet deeper than it is), no doubt the 

 entire work could be completed for little more than a tithe of the 

 cost (which was 454,700/.), and need not certainly occupy a longer 

 period than two years, as is proved by the following facts : — 



The excavation for the Thames Tunnel commenced in December, 

 1825, and all went on satisfactorily until 12th May, 1827, when, 

 the upper portion of the works protruding above the London clay 

 into the gravel and silt of the bed of the river, the first irruption 

 of water took place, there being then a length of 545 feet of the 

 tunnel constructed, which had been done in a j)eri(jd of seventeen 

 months ; so that, had no casualty occurred, and assuming that the 

 rate of progress was not, as it no doubt would have been, augmented 

 by the natural increase which always follows a better knowledge of 

 any work, the whole 1200 feet would have been completed within 



VOL. VI. 



