Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/555

1869.] WHITAKER—CONSUMPTION DEATH-RATE. 431 was brought to the sea by glaciers, or floated by ice. Most of the rounded larger stones, excepting where they are the remains of sea-beaches in situ, were carried from sea-coasts by floating ice, and dropped with or without finer drift matter into ordinary marine deposits then in course of being accumulated. In many places these deposits lay out of the way of receiving additions from floating ice.

(4) Marine deposits extend up hill-sides, cover upland valleys and plateaux, and stretch along the bases of escarpments (as in Derbyshire) where few or no erratic boulders or stones are to be found. At high levels the identity of these deposits with so-called drifts is rendered probable by the fact that the finer matter composing them is seldom entirely*, though generally mainly, of local derivation, and likewise by the fact that they graduate by imperceptible degrees into erratic drifts at lower levels.

(5) The absence of rounded stones in superficial accumulations, at high levels, may be attributed to the positions in which they occur having been unfavourable to littoral attrition, or to the sea having not continued long at a stationary level. Though the angular stones in these accumulations are local, they often occupy positions to which they must have been drifted from short distances.

(6) Unless the term drift be limited to erratic stones contained in clay, sand, and gravel, the general covering of hilly districts†, so far as it is distinct from merely fallen or washed-down detritus, freshwater alluvium, and the effect of disintegration in situ, ought to be included in the term drift deposits.

7. On the Connexion of the Geological Structure and Physical Features of the South-east of England with the Consumption Death-rate. By W. Whitaker, Esq., B.A., F.G.S.

[Abstract.]

The author stated that his investigation of this subject, which was carried on in conjunction with Dr. Buchanan, was suggested by the

graduating into sandy loam, which in some places is scarcely distinguishable from the covering of the Yoredale and Millstone-Grit strata of the neighbourhood, and both may be found graduating into drift deposits with erratic stones at lower levels. The clay on the limestone is distinct in colour and composition from the underlying coating of decomposed limestone. The latter is produced by the chemical action of the rain-water which the clay prevents from running off. Here, as in the Furness district, smoothly sculptured rock-surfaces, where they are covered with clay, are becoming minutely pitted and disfigured by pluvio-chemical action. These surfaces, under dry loam, or in the open air (where rain-water quickly runs off), are smoothly, regularly, and curvilinearly hollowed, rounded, basined, channelled, and funnelled.
 * In Derbyshire, near Buxton, the limestone is covered with a brown clay

† The marine origin of the general detrital covering of elevated areas in Scotland is admitted by Mr. James Nicol (Quart. Journ. Geol. Soc. vol. xxv. p. 283) and by Mr. James Geikie (Geol. Mag. vol. v. pp. 22, 23), who speaks of "angular Gravel" and "mounds of debris" on hill-sides as having been accumulated by the sea.