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. Thickness Depth +------ | Irregular made ground | 5 | Clayey | | Alluvium 5 +------ | 4 | Peat | 9 +------ | | | | | 10-12 | Sand and Gravel | | | | | 21 +------ 2 | +------ Gravel 2 | 25 +------ | 4'6" | Running Sand | 29' 6" +------ Gault | _Scale_ 8' to 1" [Illustration: Fig. 2. Section seen in digging foundations of Tennis Courts on Midsummer Common, Cambridge.] Lower down the river near Ely a most important and interesting section has recently been exposed. A new bridge was built over the Ouse near the railway station and to obtain material for easing the gradient up to the bridge a pit was sunk close to it on the east side of the river, and was carried down to the Kimmeridge Clay thus giving a clear section through the whole of the alluvium (Fig. 4, p. 11). Depth