Skeleton lately found at the Tilbury Docks, Essex. 137 
deposited is covered by the mud or silt in suspension in the 
turbid waters, which fills up the slight hollows and produces 
the flatness of surface characteristic of alluvium. This 
deposition is accompanied by a corresponding rise in the bed 
of the river. The fragments of former alluvial deposits, found 
as terraces at various heights on the sides of the valleys of 
the Thames and other rivers, mark the levels at which the 
stream once flowed, the highest terrace being the oldest. 
These terraces are the remains of broad continuous sheets of 
ancient alluvium deposited under much the same circumstances 
as those in which the lowest flats are now being formed. An 
upheaval occurring would increase the fall of the river, and 
cause it to deepen its channel. In doing so it would destroy 
much of its old alluvial plain, and, sooner or later, cut its 
way downward to a point at which it would again cease to 
deepen its bed, and would form another flat at a lower level 
than the first ; and so on. 
Tilbury Docks are being made in the newest of the river- 
deposits of the Thames Valley, the alluvium of the marshes, 
the deposition of which would still be going on, but for the 
embankment of the Thames during (or before) the Eoman 
occupation of Britain. An average section of the beds visible 
(May, 1884) would give 
Blue Clay ... 
about 7 ft. 
Upper Peaty Bed ... 
„ 1ft. 
Blue Clay ... 
„ lift. 
Lower Peaty Bed ... 
5 ft. 
Blue Clay ... 
„ 7 ft. 
Sand, and Gravel ... 
31 ft. 
But though only two peaty beds were visible in the dock- 
excavations, we were informed by Mr. J. B. Pinker, the 
gentleman connected with the works who explained their 
plan during our excursion in May, that a third and still 
lower peaty bed had been met with here and there in the 
trial-borings made within the dock area. This third bed 
is noted in the account of the section of the New Well at 
