Mr. J. M. Fraser, in a paper which he read at the Institution of Civil Engineers, on the 24th of March, 1863, considered, that “it would not be inaccurate to assume 80 miles as representing the length of tunnels now daily traversed by railway trains in the United Kingdom.” At that period there were 11,547 miles of railway in operation. As there were 13,882 miles opened for traffic on the 31st of December, 1866 (of which about one-third is single line), we may consider that w e have about 90 miles of line “in tunnel” at the present date, and in these are included the Metropolitan (Underground) Railway and the tunnels[127] on the New Midland Line between Bedford and London, opened for goods traffic in August 1867. We knew as a fact that, during the early construction of railways in England, our engineers resorted to tunnels to avoid gradients and curves (especially the former) that would almost be considered favourable at the present day. As experience increased and the power of the locomotive was developed, so did the amount of tunnel work diminish. Hence it is that if the three estimates just stated be correct, the proportion of tunnel to railway on the 1st of January, 1856, was one mile to every 115; on 1st of January, 1863, one to every 144 miles; on 1st of January, 1867, one to every 154. Had Ireland been excluded from the reckoning,—as she might well be, seeing that there are only three there of the aggregate length of 2,980 yards (exactly 100 yards less than a mile and three-quarters) on the 1,948 miles of railway that are now open for traffic in that part of the United Kingdom,—the proportion of tunnel to railway in England, Scotland, and Wales would have been one mile of the former for every 132½ of the latter. The number of tunnels in Ireland is, however, it is alleged, about to be added to, as, since a very serious accident at “Bray Head,” on the Dublin, Wicklow and Wexford Railway, a feeling of uneasiness prevails in the public mind as regards the safety of the line at this point. It is, therefore, contemplated to run four tunnels through the mountain at its side nearest to the sea, at an estimated cost of about £23,000. Bray Head, it may be mentioned, forms the southern boundary of the Bay of Dublin, the Hill of Howth being its boundary to the north. The longest railway tunnel in England[128] is the Woodhead or Summit Tunnel of the Manchester, Sheffield and Lincolnshire Railway. Its length is 5,296 yards, or 3 miles and 16 yards, with a gradient of 1 in 200, or 26⅖ feet to the mile, the rise being in the direction from Dunford to Woodhead. The ordinary passenger trains require ten minutes from Dunford to Woodhead, but trains travelling from Woodhead to Dunford take a minute less. Therefore, with the gradient favourable, the speed is only at the rate of 20 miles an hour; against the gradient, 18. It is a single line tunnel.