The steam engine familiarly explained and illustrated; with an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain maxims for railway speculators. By the Rev. Dionysius Lardner ... With additions and notes by James Renwick ...

PLAIN RULES -FOR RAILWAY SPECULATORS. 317
behind it the impure air which it produces, and the passen
gers will be enveloped in it before it has time to ascend the
shafts. Sufficient magnitude, however, may be given to the
tunnel to prevent any injurious consequences from this cause.
A disagreeable and inconvenient odour will be experienced.
XXVIII.
Tunnels on a level, the length of which do not exceed a
third of a mile, will probably not be objectionable. Tunnels
of equal length upon acclivities would be more objection
able.
I may observe generally that we have as yet little or no
experience of the effect of tunnels on lines of railroad worked
by locomotive engines, where there is a large intercourse of
passengers. On the Leicester and Swannington railroad,
there is a tunnel of about a mile long, on a part of the road
which is nearly level; it is ventilated by eight shafts, and I
have frequently passed through it with a locomotive engine,
Even when shut up in a close carriage the annoyance is
very great, and such as would never be tolerated on a line
of road having a large intercourse in passengers. This railroad is chiefly used to take coals from some collieries near
Swannington, and there is no intercourse in passengers upon
it, except of the labouring classes from the adjacent villages:
the engines burn coal, and not coke; and they consequently
produce smoke, which is more disagreeable than the gases
which result from the combustion of coke. This tunnel
also is of small calibre.
On the Leeds and Selby railroad there is a tunnel, on a
part which is nearly level, the length of which is 700 yards,
width 22 feet, height 17. It is ventilated by three shafts of
about 10 feet diameter and 60 feet high. There is an intercourse of passengers amounting to four hundred per day
upon this road, and, generally speaking, they do not object
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