A HISTORY OF NORTHAMPTONSHIRE developed and old ones permanently deserted. These old valleys filled in with Boulder Clay or Glacial Gravel have, not inaptly, been called buried valleys. Buried Valleys Buried valleys are by no means uncommon, but only occasionally can they be traced for a sufficient distance to make out the original source and particular destination of the water they carried, for they are not noticeable till the ground is opened. A buried valley near Northampton extends from the Wellingborough Road to the Billing Road, under Abington Abbey, and evidently debouched into the Nene. The trough is some 200 yards wide, depth unknown, and is filled with a jumble of materials not greatly water-worn, none being older than the Northamp- ton Sand. On the Wellingborough Road Great Oolite limestone largely preponderates, on the Billing Road there is more clay, and Kimeridge Clay fossils are rather abundant. At Furtho, towards Stoney Stratford, an old valley of the Ouse has in its midst Boulder Clay to a thickness of 100 feet or more, which the small post-glacial streams have not been able to remove.' Numerous sand and gravel deposits would probably come under this head, including the sand beds in the parishes of Milton and Courteenhall referred on page 23. The Nene Valley The following remarks with respect to the Nene valley would apply, with modifications, to the Welland or other large watercourses. If we stand on any of the bounding hills of the Nene valley below Northampton and look at the deep, wide excavation, and then at the thin, scarcely dis- tinguishable stream meandering through the flat meadows, and if we fur- ther take account of the occasional great floods, it is difficult to conceive that the river and the floods could have produced the results observed, for the river has little or no excavating power, and floods generally, if not always, deposit more silt in the valley than they carry away out of it ; in fact the river and the valley are misfits. Now since the drainage area above any selected point was never more, and even may have been much less than now, we have to look back for a suitable time and adequate cause for a small river in a large valley, and both we find at the end of the first stage of the Glacial and the beginning of the Inter-glacial periods. The rapid melting of the first ice sheet, which left a capping of gravel over even the flat lands of the county, produced floods immense in volume and of great velocity in this valley, being perhaps equivalent in effect to a heavy rainfall over the whole watershed for a very long time, at first without any exposed porous rocks to help in its disposal by absorption, and later only saturated ones. These floods carried away all the finer material of the glacier ice, deepened the valley by excavating the clay bottom, widened it by washing away the sides, in which they were aided by frequent slips of the ' Beeby Thompson, ' Pre-glacial Valleys in Northamptonshire,' Journ. North. Nat. Hist. Soc, vol. ix. p. 47 (June, 1896). 28
