328 JOURNAL OF THE PLYMOUTH INSTITUTION. 
is more remarkable, as it not only accommodates a railway, but 
also cart and carriage roads and footways. 
Of Tunnels, we have two remarkable ones — the one under the 
Mersey, connecting Liverpool and Birkenhead ; and that under 
the Severn, connecting the towns of Bristol and Cardiff and 
Swansea, and South Wales and the West and South of England. 
The Mersey Tunnel is 2 J miles long, of which three-quarters of 
a mile is under the bed of the river ; and cost, with connecting 
railways, £1,000,000. 
The Severn Tunnel is one of the greatest engineering feats 
executed in Great Britain. Begun sixteen years ago, it has just 
been completed under enormous difficulties. Without the en- 
gineering appliances invented within the last few years and during 
its construction, it would have been almost impossible to contend 
with the noodings by land-springs and tidal waters, let in through 
fissures in the rock. It runs 2J miles under the river Severn, is 
50 feet below the deepest part of that river, and cost £2,000,000 
in construction. 
Another great engineering work affecting our locality is the 
Tilbury Docks, opposite Gravesend. They are of large extent, 
and allow of the largest ships entering at low-water, without 
having to wait for the tide, as at Liverpool and elsewhere, thus 
avoiding the difficult and dangerous navigation of the Thames, 
and enabling ships to fix times of departure irrespective of tide. 
If, as it is hoped, in addition to the Australian traffic by the 
Orient and other lines, which now start thence, it attracts the 
American lines, it will be most advantageous to us, as the steamers 
will call here, and thus save to passengers 300 miles of the 
Channel — of which Mr. Froude says, "In all the world there is no 
more uncomfortable stretch of water than the English Channel in 
nasty weather" — as well as the danger of such a crowded arid 
narrow thoroughfare. 
There are many great engineering works projected or in 
course of construction, such as the canal through the Isthmus of 
Corinth, to connect the iEgean with the Adriatic Sea ; that from 
the mouth of the Elbe to Kiel, large and deep enough to enable 
German ships of war to pass from the Baltic to the North Sea, 
and avoid the long and dangerous passage round Denmark ; the 
canal connecting Amsterdam with the North Sea, costing 
