This paper is illustrated by a section laid down from actual measurement, of 554 feet in thickness, taken in the Esk valley, near Whitby, Yorkshire, ( see page 100.) The section, geologically speaking, comprises part of the lower Oolite, the upper and part of the lower Lias. I will remark on such as are of most value. 2.—The freestone is very valuable, generally speaking, on account of its texture, colour, and large sized blocks; and has been extensively worked for upwards of 50 years, and sent from Whitby, by shipping, for the construction of piers, breakwaters, &c., in nearly all parts of the United Kingdom. 9. Oolitic Ironstone. —This seam of ironstone is very valuable for smelting purposes, but varies very much both in quantity and quality ; in some places showing a thickness of 20 and even 30 feet, containing only from 15 to 20 per cent, of iron, and a large proportion of silica; and in other places, from 5 to 12 feet in thickness, containing from 30 to 40 per cent, of pure iron, with only a moderate percentage of silica. This seam of ironstone has only been known and worked for about eight years. It is, however, now worked very extensively, and sold to the iron smelters, principally in Newcastle, for the purpose of mixture with the argillaceous ores of the lias. Its principal advantage is on account of its being more easily fluxed in the furnace. 10. Upper Lias, —Consisting of aluminous shale, cement stone, ...