Redland, near Bristol, to Alverston, on the north. It will be perceived that if the denuding causes, which have removed so much of the deposits of a later geological date than these old shingle beaches, had carried off all traces of them in the section near Compton Martin, Mendip Hills (fig. 165), so that a surface corresponding with the line d d, had only been exposed, there would have been great difficulty in assigning the different parts of this shingle (now conglomerate) covering to their relative geological dates; though, with the old mud and sands outside of them, deposited at successive times, the relative date of the parts is sufficiently obvious. While on the subject of this district, it may not be uninstructive, as it is one fertile in information, within so very small an area, to call attention to the successive coatings of fossiliferous accumulations as they followed one another, each spreading over a part of a preceding deposit, as the dry land of the Mendip Hills and adjacent country sank, and as it would appear, gradually, beneath the sea. For this purpose the accompanying map (fig. 167) may be useful. In it the different deposits represented consist, in the ascending series, of (1) old red sandstone; (2) carboniferous or mountain limestone; (3) coal measures; (4) dolomitic or calcareo-magnesian conglomerate and limestone; (5) the new red sandstone and marl; (6) lias; (7) inferior oolite, and others of the lower part of the series, known as the oolitic or Jurassic; and (8) alluvial accumulations, deposits from branches of the adjacent British Channel, where these found their way amid the sinuosities of the land, often covering a plain whereon forests once grew, at a higher relative level of sea and land than now exists, the outcrops of these sheets of concealed vegetable matter and trees forming the "submarine forests" of Stolford and other places on the present coast (p. 448).* The darkly-dotted patches in the map (conglomerates, 4) will serve to show the mode of occurrence of the beaches surrounding * The names of the various places marked by crosses and letters in the map (fig. 167) are as follow:-a, Tickenham; b, Nailsea; c, Chelvey; d, Brockley; e, Kingston Seymour; f, Wrington; g, Nempnet; k, Congresbury; 1, Banwell; m, Locking; n, Bleadon; o, Lympsham; p, Burington; q, Compton Martin; r, Hinton Blewet; s, East Harptree; t, Lilton; v, Chew Stoke; x, Chew Magna; y, Stowey; a', Shipham; b', Biddesham; c', Badgworth; d, Weare; e', Axbridge; f', Chapel Allerton; g', Chedder; h', Priddy; ", Binegar; k', Chewton Mendip; l', Wedmore; m', Radstock; n', Kilmersdon; o, Draycot; p', Stoke Rodney; q', Westbury; r', Wookey; s', Dinder; t', Crosscombe; v', North Wooton; w', Wells; x', Shepton Mallet; y, Downhead; z', Mells; a", Elm; b", Whatley; c", Nunney; d", Cloford; e", East Cranmore; and ƒ”, Chesterblade. the older rocks of the Mendip Hills, and an adjoining portion of country near Wrington, f. Although, from the travelling upwards of continuous portions of these beaches during the gradual submergence of the dry land, and the subsequent wearing of the rocks, including all in the district, up to the time of its alluvial plains inclusive, they may not give the exact representation of the beaches of one time, they will still serve to show the manner in which they were accumulated round this old portion of dry land. Taken in connexion with similar facts observable even so near as Gloucestershire and Glamorganshire,* and looking at the size of the rounded fragments sometimes found in them, the effects of considerable breaker action is observable on the shingles, and they seem to have been well piled up at the bottom of old bays and other localities where favourable conditions for their production existed. The following section (fig. 168) will show one of these Fig. 168. a a, a, limestone, intermingled with sandstones and marls, of the upper part of the carboniferous limestone series of the district, brought in by a large fault, on the N.W. of the Windmill Hill, Clifton; b, boulders and pebbles, in part subangular, of the subjacent rocks, cemented by matter in part calcareo-magnesian, variably consolidated; c, conglomerate or breccia, in which the magnesio-calcareous matter is more abundant, becoming more so at d, where it further assumes the character of the more pure dolomitic limestone in which pebbles and fragments do not occur. ancient beaches facing the gorge of the Avon, near Clifton, Bristol, in a depression between Durdham Down and Clifton Hill, in which some of the rounded portions of the subjacent rock cannot be much less than two tons in weight, requiring no slight force of breaker action to move them and heap them up as now seen. The submergence of this dry land continuing while geological changes were being effected over a wide area, (in which this district occurred as a mere point,) and so that, without reference to the modifications of deposits produced elsewhere, the red sediment of the seas near the shores of the land, then above water in the area of the British Islands, was succeeded by others in and above which animal life swarmed, the beaches moved upwards on See the Geological Map, "Memoirs of the Geological Survey of Great Britain,” vol. i., pl. 2, in which a large area occupied by accumulations of this class and time will be found represented. the slopes of adjacent rocks. Thus the rolled pebbles of the latter, and of the cliffs of the time, were occasionally intermingled with the remains of the animal life then existing. Near Shepton Mallet (x', in the map, fig. 167), where the lias (6) rests both on the old red sandstone (1), and the carboniferous limestone (2), there is much of this old shingle (now conglomerate).* The following (fig. 169) is a section, exhibited close to Shepton Mallet, on the Bath road, wherein a line of pebbles (b) is strewed over the previously upturned edges of supporting carboniferous limestone (a, a), and constitutes a continuation of some more arenaceous and pebble beds, presenting much the appearance of a shore, not far distant.† Fig. 169. a a f d d 9 The lias at c, covering this pebble or shingle bed, has been thrown down (as it is termed) by a dislocation, or fault f, so that beds above that at c, are seen at d, d, d, the latter again broken through by a dislocation at g, and the whole surface of the hill being so smoothed off by denuding causes, that a gently-sloping plane is alone seen. Before we quit this section, it may be mentioned, that an observer in search of the different conditions under which fossiliferous deposits may have accumulated will here see that much less mud must have been mixed with the calcareous matter of the lias than is usual in the district, and which is to be found not far distant from this locality. The lias limestone beds (d, d, d) are here thick, for the most part, and in purity more resemble the carboniferous limestone (a, a) on which they rest, showing a cleaner state of the sea where they were formed than in those areas over which the usual mud, and muddy and silty limestones of the lias were accumulated. Coupled with the evidence of beaches, this greater freedom from mud would seem to point to the greater proximity of a shore with minor depths of sea, near and at which the waters were generally more disturbed, so that the lighter sub These conglomerates, which are abundant, and wherein the pebbles are chiefly derived from the adjacent carboniferous limestone, have been long since pointed out by Dr. Buckland and the Rev. W. Conybeare (1824), "Observations on the SouthWestern Coal District of England;" Geological Transactions, 2nd series, vol. i., p. 294. †This was well seen further up the road, in 1845, at which time some new cuttings were in progress. stances being readily held in mechanical suspension, they were easily moved away by tides and currents to more fitting situations for deposit. This character of a less muddy condition of the lias is by no means confined to the vicinity of Shepton Mallet; it is to be seen in several places in that part of England and South Wales. It is well shown in parts of Glamorganshire, where, indeed, as in the vicinity of Merthyr Mawr care is required not to confound some of the lias with the carboniferous limestone to which it there bears no inconsiderable mineralogical resemblance. Here, again, the observer finds this character in connexion with old conglomerates, resembling beach accumulations of the time of the lias, pointing to the probable proximity of dry land, such as may be readily inferred to have then existed in the great coal district on the north of it, even now, after so much abrasion, during depressions and elevations beneath and above the sea during a long lapse of geological time, rising high above these deposits. In the same neighbourhood (Dunraven) there is also good evidence of the lias reposing upon a clean surface of carboniferous limestone, as will be seen in the annexed sketch (fig. 171) and in the subjoined section (fig. 170), Fig. 170. wherein a represents disturbed strata of the latter, and 6 beds of the former, resting on their edges. In the section (fig. 170) the lower beds (6) of the lias are light-coloured, and contain fragments from the subjacent carboniferous limestone, these succeeded by argillaceous grey limestones at c. f, f are dislocations or faults, traversing the beds. In this case, though an observer might suspect the vicinity of a coast from the fragments in the lower lias, he would desire further evidence, and by search he would find, Fig. 172. d a round the point d, in the sketch (fig. 171), a conglomerate (b, b, fig. 172), reminding him of a beach interposed, to a certain extent |