the Birkenhead 5,040 gallons per minute; and as these pumps will be
required for the permanent draining of the tunnel, they are constructed
in the most solid and substantial manner. They are worked by compound
engines made by Hathorn, Davey & Co., of Leeds, and are supplied
with six steel boilers by Daniel Adamson & Co., of Dukinfield, near
Manchester.

In addition to the above, there is in course of construction still
more powerful pumps of 40 in. diameter, which will provide against
contingencies, and prevent delay in case of a breakdown such as occurred
lately on the Liverpool side of the works. The nature of the rock is
the new red sandstone, of a solid and compact character, favorable for
tunneling, and yielding only a moderate quantity of water. The engineers
have been enabled to arrange the levels to give a minimum thickness of
25 ft. and an average thickness of 30 ft. above the crown of the tunnel.

Barges are now employed in the river for the purpose of ascertaining the
depth of the water, and the nature of the bottom of the river. It is
satisfactory to find that the rock on the Liverpool side, as the heading
is advanced under the river, contains less and less water, and this the
engineers are inclined to attribute to the thick bed of stiff bowlder
clay which overlies the rock on this side, which acts as a kind of
"overcoat" to the "under garments." The depth of the water in one part
of the river is found to be about 72 ft.; in the middle about 90 ft.;
and as there is an intermediate depth of rock of about 27 ft., the
distance is upward of 100 ft. from the surface of low water to the top
of the tunnel.

It is expected that the work will shortly be pushed forward at a much
greater speed than has hitherto been the case, for in place of the