EXPLANATION OF THE PLATES

xv

Pi .ate XXIII. Curved strata and Sand-pit in Headen Hill, Alum Bay, I. W.

T. W. del.

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This view was sketched in the year 1811. At that time a pit was dug in the finewhit, sand under the curved stratum of soft calcareous rock that appears above it,and which afterwards proved to be the lower freshwater formation. But as thesesand pits founder, and are filled up every winter, on revisiting the spot in thefollowing summer, the place could scarcely be recognised. The whole of the curvedparTof the stratum over the sand-pit, as seen in the present sketch, had fallen downwith the pit, and had disappeared ; but as the new face presented a similar section,the facts remained the same ; and as the etching was finished, it was not considerednecessary to make a new one corresponding to its second appearance, since eachsucceeding winter produces such alterations in these cliffs, that any details of formobserved one year, would be obliterated the next. When the first sketch was made,the stratum of black clay immediately under the curved stratum, was not so evidentas at present; this has therefore been strengthened. The stratum to the right isthe yellowish sand, dipping about 45°, adjoining to the vertical strata. Over thecurved stratum is part of the upper marine marie that had slid down from above, andbeyond is the upper freshwater formation, forming lofty cliffs, removed a littleback. See page 159, 160.

Plate XXIV. This sketch was made at the same time as the last, and is a nearer (Lo /view of the curved part. It must be observed, that in the succeeding state of thecliff, the curvature appeared still greater than in the present sketch. The dark tintof the clay under it has also been added. .See page 159.

Plate XXV. Scratched Bay and the Needles, I. W. T. W. del. ^

This view is taken from a small rock that makes its appearance at low-water, alittle to the north of the middle needle. It is seen in the foreground, and is thestump of the lofty spire of chalk which gave the name to these rocks, but which,being worn through by the sea, fell down in the year 1764. From this spot, onwhich it is seldom practicablejUoA&id, the lofty perpendicular chalk cliffs present adistinct section of the middle range of hills in this island, and the dip of the stratamay be accurately observed, being nearly vertical towards the north or left side, andleaning more and more towards the south side. To the left is Alum bay. A smallpart only of the clay cliffs are included in this plate, shewing their junction with thechalk. The coloured view, No. 3. PI. XIX, of the whole of the cliffs of Alum bayand Headen, was drawn from the same station, and being on the same scale, may be