HAMBURG DOCKS.
43
there is 35 to 40 feet deep at low water spring tides, having an almost
vertical face in places on its northern side, the depth increasing suddenly
flom 5 to 30 feet, owing to the scour of the tidal current against this side,
the channel having been eroded by it out of the hard clay of the ‘ Hebbles,’
a shoal extending J mile above and 2 miles below the Alexandra Dock.
Ihe Hebbles shoal is mostly composed of very hard boulder clay, with large
Fig. 12. —Alexandra Dock, Hull.
boulders reaching up to J ton in weight, and smaller stones strewn over
the surface, and beds of peat were also found.”* The original surface of
the foreshore and river bed and the deepening effected by the dredging
operations previous to the opening of the dock for traffic are shown on the
plan in fig. 12.
Hamburg Docks.
Lhe town of Hamburg is situated 62 miles above the outlet of the river
be. As in the case of Glasgow, the range of tide, which averages 6 feet,
not sufficient to render gates an absolute necessity, and they have been
ispensed with, although the maximum difference between high and low
"ater reaches 19| feet. One reason which operated in favour of this
ecision was that locks would have seriously hindered the considerable
tiaffic between sea-going ships and the river boats which ply between
Hurtzig on “ The Alexandra Dock, Hull,” Min. Proc. Inst. C.E., vol. xcii.