86
T. M. BEADE ON THE DBJET-BEDS OE THE
Pig. l. — Plan of Atlantic Doclcs, Liverpool, 1874-81.
J I II II IU
Branch Dock No. 3; and here the Boulder-clay was again exposed. In
the trench for the dock- wall parallel with the river-wall the surface
of the Boulder-clay was 16 feet below ordnance datum. The section
disclosed 9 feet of Boulder-clay, 3 feet of sand occasionally developing
into gravel, and then from 3 to 5 feet of Boulder-clay resting on red
sand and red "roach" rock.
A Postglacial gully excavated in the Boulder-clay intersected
the dock ; and in this was the trunk of an oak tree, about 3 feet in
diameter, lying longitudinally in the gully, as if it had been washed
down it, at a level of about 22 feet below high water ; a layer of
recent silt covered the whole.
In May 1876 further excavations showed below the silt a con-
siderable thickness of peaty matter full of drift timber, principally
oak and pine. In one place only, at the base of the peat, I observed
the stump of a tree rooted into sand resting upon the Boulder-clay.
At various times between 1876 and 1878 I carefully examined
the excavations of the series of docks and graving-docks, extending
over an area of about 80 acres, and made record sections of the beds
disclosed : these I reproduce (figs. 2-5, p. 88), as they will serve to
explain the drift-geology better than any written description*.
It must be understood that the beds are so irregular that another
observer coming at a time when a different face was exposed
would no doubt give a different representation of it. The sections
I give I considered typical ; and I vouch for their accuracy.
Speaking generally, the same succession prevails as occurred in the
sections already described. In ascending order we have the red
rock of the Trias with the red sand and rubble covering it ; upon

• I must here express my indebtedness to Mr. Gr. F. Lyster, the engineer to
  

the Mersey Docks and Harbour Board, for the facilities of inspection afforded