In digging the foundations for the chimney of the Electric Lighting
Works opposite Magdalene College the following section was seen (Fig.
1, p. 8).
Under the new Tennis Courts in Park Parade facing Mid-summer Common the
section was somewhat different (Fig. 2, p. 9).
While in the pit dug some years ago by Mr Bullock at the other end of
the Parade at the lower end of Portugal Place in the south-east corner
of the Common there was a section very similar to the last (Fig. 3, p.
10).
+------
| Made ground
|
| 7'-8'
|
+------
| Black silt
|
| 7'-8'
|
+------
| 4' Peaty silt
|
+------
| 4' Gravel
|
+------
| Gault
|
[Illustration: Fig. 1. Section seen in foundations of chimney for
Electric Lighting Works near river opposite Magdalene College, July,
1892.]
These three sections, immediately north of Cambridge where the valley
of the Cam opens out on to the Fens, are important as showing the
variations right across the alluvium from side to side and the absence,
here at any rate, of any indication of a constant sequence distinctly
pointing to important geographical changes. A section seen under
Pembroke College Boat House gave 16 feet of clay and peaty silt on the
black gravel which here, as in the borings at the Backs of the
Colleges, forms the base of the alluvium. About half way down were
bones of horse and stag, but I do not believe that these are of any
great antiquity, probably not earlier than mediaeval.