TRANSACTIONS OF SECTION G. 657 



SO that each station should he on the summit of a bill. An ideal railway would 

 have gradients of about 1 in 20 falling each way from the stations with a piece of 

 horizontal connecting them. With such gradients gravity alone would give an 

 accelerating velocity to the departing train at the rate of one mile per hour for every 

 second ; that is to say, in half a minute the train would have acquired a velocity 

 of thirty miles an hour, whilst the speed of the approaching train would he corre- 

 spondingly retarded without the grinding away of hrake-hlocks. t'ould such an 

 undulating railway be carried out, the consumption of fuel would probably not 

 exceed one-half of that on a dead level railway, whilst the mean speed would be 

 one-half greater. Although the required conditions are seldom attainable in prac- 

 tice, the broad principles should be kept in view by every engineer when laying out 

 a railway with numerous stopping-places. 



Nearly thirty j-ears ago, when projecting the present system of underground 

 railways in the metropolis, I foresaw the inconveniences which would necessarily 

 result from the use of an ordinary locomotive, emitting gases in an imperfectly 

 ventilated tunnel, and proposed to guard against them by using a special form of 

 locomotive. When before the Parliamentary Committee in 1854, I stated that I 

 sliould dispense with firing altogether, and obtain the supply of steam necessarj- for 

 tlie performance of the single trip between Paddington and the City from a plain 

 cylindrical egg-ended boiler, which was to be charged at each end of the line witli 

 water and steam at a liigh pressuie. In an experimental boiler constructed for me, 

 the loss of pressure from radiation proved to be only .'jO lbs. per square inch in 

 five hours, so that practically all the power stored up would be available for use- 

 ful work. I also found by experiment that an ordinary locomotive with the fire 

 ' dropped ' would run the whole length of my railway witli a train of the required 

 weiglit. Owing to a variety of circumstances, however, tliis hot-water locomotive 

 was not introduced on tlie Metropolitan Railway, though it has since been success- 

 fully used on tramways at New Orleans, Paris, and elsewhere. I am sorry to have 

 to admit that the progress of mechanical science, so far as it affects locomotives for 

 underground railways, has been absolutely nil during the past thirty years. The 

 locomotive at present employed is an ordinary locomotive, worked in the ordinary 

 way, except that in the tunnel the steam is condensed, and combustion is aided by 

 tlie natural draught of the chimney alone, instead of being urged by a forced blast, 

 as on open portions of the line. Whether a hot water, a compressed air, or a com- 

 pressed gas locomotive could be contrived to meet the exigencies of metropolitan 

 traffic is a question wdiich, I think, might be usefully discussed at the present or 

 some future meeting of the Association. 



A reference to the underground railway naturally suggests the wider question 

 of tunnels in general. The construction of tunnels was not one of the novelties 

 presenting itself to railway engineers, for many miles of tunnel had been driven by 

 canal engineers before a single mile of passenger railway had been built in this 

 or any other country. To foreign engineers belongs the honour of liaving boldly 

 conceived and ably accomplished tunnel works of a magnitude which would have 

 appalled a canal engineer. I need only refer to the Mont Cenis Tunnel, over 

 7^ miles in length, commenced in 1857 and finished in 1870; the St. Gothard 

 Tunnel, 9| miles in length, commenced in 1872 and finished in 1882; and the 

 Hoosac Tunnel, 4J miles in length, commenced in 1854 and finished in 1875. In 

 all cases rock of the hardest character had to be pierced, and it is needless to 

 remark that without the aid of the machinist in devising and manufacturing 

 compressed air machinery and rock-boring plant the railway engineer could not 

 have accomplished his task. Intermediate shafts are not attainable in tunnels 

 driven through great mountnin ranges, so all the work has to he done at two faces. 

 In the case of the Mont Cenis Tunnel the mean rate of progress was 257 feet and 

 the maximum 400 feet per month. In the St. Gothard Tunnel the mean rate was 

 429 feet and the maximum 810 feet. In the Hoosac Tunnel the average rate was 

 150 feet per month. 



Tunnels under broad navigable rivers and estuaries have been a subject of 

 discussion by engineers for at least a century, but the only one at present com- 

 pleted is the unfortunate and costly Thames Tunnel. Two important works of the 

 1882. u u 



