Mr. Smiles, in his _Life of George Stephenson_, remarks:—“Sanitary
objections were also urged in opposition to railways, and many wise
doctors strongly inveighed against tunnels. Sir Anthony Carlisle
insisted that “tunnels would expose healthy people to colds, catarrhs,
and consumption.” The noise, the darkness, and the dangers of tunnel
travelling were depicted in all their horrors. Worst of all, however,
was ‘the destruction of the atmospheric air,’ as Dr. Lardner termed it.
Elaborate calculations were made by that gentleman to prove that the
provision of ventilating shafts would be altogether insufficient to
prevent the dangers arising from the combustion of coke, producing
carbonic acid gas, which in large quantities was fatal to life. He
showed, for instance, that in the proposed Box tunnel, on the Great
Western Railway, the passage of 100 tons would deposit about 3090 lbs. of
noxious gases, incapable of supporting life! Here was an uncomfortable
prospect of suffocation for passengers between London and Bristol. But
steps were adopted to allay these formidable sources of terror. Solemn
documents, in the form of certificates, were got up and published, signed
by several of the most distinguished physicians of the day, attesting the
perfect wholesomeness of tunnels, and the purity of the air in them.
Perhaps they went further than was necessary in alleging, what certainly
subsequent experience has not verified, that the atmosphere of the tunnel
was ‘dry, of an agreeable temperature, and free from smell.’ Mr.
Stephenson declared his conviction that a tunnel twenty miles long could
be worked safely and without more danger to life than a railway in the
open air; but, at the same time, he admits that tunnels were nuisances,
which he endeavoured to avoid wherever practicable.”