Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/305

1870.] WILSON RUGBY SURFACE-DEPOSITS. 197 what seem to be detached, are seen in the gravel ; but I have never been certain of a single case of detachment. Stones are found imbedded in the upper and under surfaces of the clay, notably the latter ; I have found no striated stones here. The drift is of the usual character — quartzose pebbles and grits, and flints, in about equal quantities, and sand, which lies sometimes in patches. Some of the stones here are large, one or two feet in circumference.

Continuing to skirt the plateau we come next to that arm of the hill which runs between the Lawford and Bilton roads. By the side of the road from Old Bilton to New Bilton is an excavation, in the upper part of which sand is worked, and in the lower clay. The sand caps the hill, and is of the usual character ; it is overlain by a remarkable deposit about 5 feet thick where it is now exposed, consisting of marly clay, with pebbles very evenly interspersed through its whole thickness. The most frequent are chalk ; and these are generally well striated. The clay is in some cases sufficiently mingled with sand to allow of the percolation of water ; and in consequence the chalk is here in a state of powder. There is a block of syenite of considerable size lying on the surface there, and a still larger block, weighing several hundred pounds, of grit, smoothed and striated longitudinally.

The clay with chalk pebbles is very partial on this hill, as far as I know ; but the sand continues along the brow of the hill to Rugby.

The Dunchurch-Road Pit, higher up the same side valley, and on the same side of it, offers a very instructive section. In March 1869 there was exposed a face of undisturbed Lower Lias clay, containing a few ammonites, &c. ; on it rested a stiff brown clay containing many stones, but principally blocks of chalk. I obtained grit (sometimes in large blocks ; one was 2 feet long and 1 foot 9 inches broad and high), Oolitic blocks, Lias, many flints, and quartzite pebbles. The chalk is found in pieces of all weights, from 1 cwt. down to dust, the particles of which can only be detected by a microscope. All the larger pebbles are grooved.

The sand is slightly stratified, sugary, and contains grains of chalk universally. In some places crumbling pieces of chalk can still be seen. Mr. Pike reports that 12-1/2 percent of an average specimen consisted of carbonate of lime and sesquioxide of iron. Above the sand is the usual flinty and quartzose drift, here thin, but higher up the hill successively 6, 10, and 13 feet thick. The drift is entirely wanting a little lower down the slope. The surface of the Boulder- clay here is very uneven ; of the Lias clay generally even.

The next arm of the same plateau is that on which Bilton stands. This closely resembles the rest. At the vicarage at Bilton is 2 or 3 feet of gravel and then 23 feet of sand, this being on the slope of the hill ; at the top is 13 feet of gravel over clay. Near the Blue Boar, at Canston, and elsewhere in the neighbourhood, we meet with from 5 to 15 feet of gravel, resting on clay with pebbles and sand, and finally on Lias clay. Towards Frankton and Church Lawford