The boulder clay at the seaward end of the Vale seems to have been capped by ice of a thickness of nearly 100 feet which efficiently contained the waters of the lake until they overflowed through a depression among the hills to the south of Malton. If the waters escaped by any other outlet to the west near Gilling and Coxwold, it can scarcely have been more than a temporary affair compared to the overflow that produced the gorge at Kirkham Abbey, as the Gilling Gap was itself closed by the great glacier descending the Vale of York. The overflow of the lake by this route, south of Malton, must have worn a channel down to a lower level than 130 feet O.D. before the ice retreated from the seaward end of the Vale, otherwise the escape would have taken place over the low hills blocking the valley in that direction and the normal course of the drainage of the country would have been resumed. The southern overflow evidently dug its way through the hills fast enough to maintain that outlet, and at the present time the narrow gorge at Kirkham Abbey is only 50 feet above sea level, and the hills through which the Derwent passes at this point are from 200 to 225 feet high. [Illustration: A Map of North-Eastern Yorkshire showing Lake Pickering during the maximum extension of the ice. The area covered by ice is left unshaded. The arrows show the direction of the glacier movements. (Reproduced from the _Quarterly Journal of the Geological Society_, by permission of Professor Percy F. Kendall.)] As the waters of the lake gradually drained away, the Vale was left in a marshy state until the rivers gradually formed channels for themselves. In recent times drainage canals have been cut and the streams embanked, so that there is little to remind one of the existence of the lake save for the hamlet still known as The Marishes. The name is quite obviously a corruption of marshes, for this form is still in use in these parts, but it is interesting to know that Milton spelt the word in the same way as the name of this village, and in Ezekiel xlvii. II we find: "But the miry places thereof, and the marishes thereof, shall not be healed." The ease with which a lake could again be formed in the Vale was demonstrated in October 1903 after the phenomenally wet summer and autumn of that year, by a flood that covered the fields for miles and in several places half submerged the hedges and washed away the corn stooks. The evidence in favour of the existence of Lake Pickering is so ample that, according to Professor Kendall, it may be placed "among the well-established facts of glacial geology."[1] [Footnote 1: _Quarterly Journal of the Geological Society_, vol. lviii. part 3, No. 231, p. 501.]