+---------- High water (12' 6" above O.D.) | 12' 6" | 12' 6" +---------- Ordnance Datum 4' 0" | Silt and clay 16' 6" +---------- {| {+---------- Low water (6' 0" below O.D.) {| {| 19' 6"{| {| {| {+---------- Bed of river (17' 6" below O.D.) {| 36' 0" +---------- | | | 9' 0" | Sand with shells | | | 45' 0" +---------- 3' 6" | Loam and sand 48' 6" +---------- | 5' 6" | Ballast with shells | 54' 0" +---------- 3' 6" | Loam with Peat 57' 6" +---------- 3' 6" | Fine red ballast | mixed with clay 61' 0" +---------- 5' 0" | Blue and grey clay | mixed with sand 66' 0" +---------- 1' 0" | Ballast 67' 0" +---------- | 4' 6" | Silty Sand 71' 6" +---------- | Ballast with flint 1' 6" | and stone 73' 0" +---------- | | | Stiff grey clay | | [Illustration: Fig. 5. Section seen at Sutton Bridge.] Here again we see that the only peat is a bed between three and four feet in thickness of mixed loam and peat more than 40 feet below mean sea level. From these sections it is clear that along the direct and more permanent outfall from Cambridge to the north, peat forms but a small part of the Fen Beds. Peat is a substance of so much value as fuel, of such importance to the agriculturist, of such commercial value in what we may call its by-products, and of such scientific interest in the history of its formation and the remains which its antiseptic properties have preserved, that it has, as might be expected, a large literature of its own. I have before me a list of more than 150 references to peat or to the Fens. PEAT; TREES AND OTHER PLANTS; TARN PEAT AND HILL PEAT; BOG-OAK AND BOG-IRON.