part of Holderness, meeting and blending with the inland native glacier on the Humber; and the vast united ice-stream thence pursued its onward southern course, enfolding everything in its icy embrace, to the Thames and to the Severn. {89b} These great ice-streams created the geological formation called “The Drift,” or boulder-clay, which we have at Woodhall. The clay is simply the _detritus_, produced by the grinding, through long ages, of the rocks under the vast and weighty ice-fields slowly moving over them, and the abrasion of the hill-sides which they scraped in their course. The boulders are detached fragments, which fell from various rocky heights overhanging the ice-stream, rested on the surface of the ice-sheet, were borne along by it through hundreds of miles, and when, in the course of ages untold, the climate became milder, and the glaciers gradually shrunk and eventually disappeared, these fragments, often bearing the marks of ice-scraping, and oftener rounded by ice-action, fell to the soil beneath, and remain to this day, to bear their silent witness to the course once taken by the giant ice-stream. The period through which this process was going on has been variously computed, from 18,000 years, according to the estimate of Major-General A. W. Drayson, F.R.A.S., who gives elaborate astronomical statistics in support of his views (Trans. Victoria Institute, No. 104, p. 260), to 160,000, as calculated by Mr. James Croll (“Climate and Time”). It is now generally held that there were more than one ice-age, with inter-glacial breaks. These boulders are abundant in our neighbourhood, and of all sizes. They may be measured by inches or by yards. There is a good-sized one in the vicarage garden at Woodhall Spa, which the present writer had carted from Kirkby-lane, a distance of a mile and a half. There is a larger one lying on the moor, near the south-east corner of the Ostler Ground. The writer has one in his own garden, a large one, more than 6ft. in length by 3½ft. high, and 2½ft. thick. It took five horses to drag it from its position, a quarter of a mile distant. There are six visible in the parish of Langton, two or three large ones near Old Woodhall Church; several large ones in Thimbleby, Edlington, and elsewhere. Smaller ones are often to be seen placed at turns in the roads to prevent drivers running their vehicles into the bank, or used as foundations to old cottages or farm buildings; and still smaller specimens may be constantly picked up by the pedestrian, or the sportsman, in his rambles through the fields. Much interest has of late years been taken in these boulders, arising from the distinct classes of glaciers to which I have referred, and the consequent difference between the nature of the boulders, as well as the source from which they have come, according as they belong to the one class or the other; and our Lincolnshire Naturalists’ Union have now