Leonard Horner

“ The coast between Watchet and Blue Anchor is composed of the red rock with grey patches, similar to that in the eastern part of the district, of another variety of it containing gypsum, of a blackish indurated clay traversed by gypsum, and of the lyas strata. All these appear in the cliffs and on the shore at different intervals, but the great disturbances in the stratification have thrown the whole into such confusion that I found it impossible during my stay to come to any satisfactory conclusion as to their relative positions. ”

“ Very often a slender thread cuts across a thick vein, throwing it several inches out of its regular course, affording a miniature representation of the disturbances in the great veins of mining districts. These veins do not penetrate the slate either above or below the stratum of limestone in which they are contained: but there are other veins of calcareous spar which cut through the strata, generally occasioning a dislocation, and in many instances I observed the substance of the vein penetrating the adjoining strata in minute ramifications. ”

“ In passing through the village just named, I observed in the street a small block of stone differing in appearance from any I had found previously, and upon examination I found it to be granite, a rock I had searched for before without success, and indeed this is the only place where I saw an unstratified rock in the whole district, the porphyry and greenstone which accompany the grauwacke formation in Devonshire being wholly wanting here. ”

“ Thin layers, composed of quartz, chlorite, and ferriferous carbonate of lime, are often interposed between the strata of slate, and pyrites is sometimes disseminated through the mass of the rock. Copper, in the state of sulphuret and of malachite, and veins of hematite, are frequently found, and nests of copper ore of considerable magnitude have been found in the subordinate beds of limestone. ”

“ Vast blocks of it have fallen down, and are piled above each other and strewed along the shore; in those that are within reach of the dashing of the waves the gypsum is nearly washed out, giving them a very singular appearance. The rock is not distinctly stratified, but the thickest veins of gypsum are parallel to each other, and nearly horizontal: it contains as usual the grey patches and stripes. The principal veins of gypsum are of different thicknesses; in some places they nearly equal three feet, and the red rock between them is penetrated by smaller veins branching off in all directions ”

“ The limestone is similar to that found in the conglomerate at Alcombe. The lower part of the valley on the south side of Grabbist hill is chiefly meadow land, but in some places where the ground is broken, as in the road near Wotton Courtney, and in the road from Timberscombe to Minehead, I observed a red marly sandstone with grey patches containing thin strata of a small sized very compact breccia composed of fragments of a white indurated clay, united by a cement of clay mixed with calcareous matter, and here and there small cavities in it lined with calcareous spar. ”

“ The whole country is so covered by vegetation, either in the form of heath and turf on the high land, or of the more luxuriant productions of the vallies, that very few opportunities occur in the interior of ascertaining the nature of the rock on which the soil rests; but the cliffs on the sea shore afford such an ample field for studying the mineralogical structure of the country, that the scattered observations in quarries, may be more strongly relied on and more easily connected. ”

“ A great proportion of these have the structure of sandstones, the component parts varying in size from that of mustard seed to such a degree of fineness, that the particles can with difficulty be discerned. Quartz and clay are the essential component parts of all the varieties, but in different proportions. The quartz in some instances prevails to the entire exclusion of any other ingredient, forming a granular quartz rock: it is more abundant in the aggregates of a coarse grain, clay being the chief ingredient in those of a close and fissile texture. ”

“ This lyas is an argillaceous limestone of a dull earthy aspect, with a large conchoidal fracture, and generally of a light slate blue colour. It occurs in very regular strata which seldom exceed a foot in thickness, and are often not more than four inches: they are separated from each other by strata of slate clay, varying considerably in thickness. All the strata of this limestone, though externally very similar, are not of the same mineralogical composition, for they have very distinct properties. ”

“ The smaller grained rock frequently alternates with the coarse conglomerate: at Tivington the latter variety prevails, but at Huntsgate that resembling a sandstone forms the thickest beds. Both varieties are very much traversed by veins of calcareous spar. At Holt farm there is a vein nearly 18 feet thick, consisting of several layers so distinct that I at first conceived the mass to be a series of strata, but upon further examination I found that it was inclined at right angles to the dip of the beds of conglomerate. ”

“ Besides this great bed, there are several others of less thickness contained in the slate, and the thinner beds are of an iron-grey colour. The slate is one of those line grained varieties which approach very nearly in appearance to the clay slate of a primary country; it is very much contorted, and the curvatures are often so small as to be seen in a cabinet specimen. Is is very much traversed by veins of quartz. I was informed by the workmen at Allercot that there are quarries of a similar kind of limestone at Westcot, Treborough and Leigh. ”

“ I observed a similar structure in the red rock, but the divisions were much smaller than in the limestone strata. In both instances the appearance is very like that of amass of dried clay or starch. When the strata of limestone are not divided into those columnar concretions, they are generally separated into large irregular shaped masses by joints perpendicular to the stratification, and in many parts they are penetrated in every possible direction by contemporaneous veins of calcareous spar crossing each other like net. work. ”

“ To those however who may give to it the theoretical meaning which this word implies in the Wernerian system, I must again point out the alternations of quartz rock, and of a clay slate, with beds of limestone full of organic remains. The clay slate cannot be distinguished from that of a primitive country. ”

“ Alterations of the fined grained slaty varieties with those of the coarsest structure in many successive strata and without any regularity of position, are of constant occurrence, and frequently without any gradation from one structure into the other. [3] In some instances portione of slate are contained in the coarse grained varieties. Scales of mica are frequent, and they all contain oxide of iron in greater or less proportion, and to the different states of this oxide their various colours are, no doubt, to be ascribed. ”

“ Within a few yards of the granite the inclination of the strata is about 35°, but as it approaches nearer to it the angle increases to 63°, and the texture of the stone becomes much more compact; the actual junction of the two rocks is, as is usually the case, very indistinct, the stratification of the slate being very much disturbed and broken: but I was informed that the best whetstones are got nearest the granite, and I found the most indurated pieces in that situation. ”

“ The fragments are of different sizes; some of them are as large as a man's head. The conglomerate is covered by a loosely aggregated quartzose sandstone, varying in colour from reddish white to brownish red, and often containing much calcareous matter. Sometimes there are fragments of the same varieties of grauwacke that occur in the conglomerate, found in those parts of the sandstone that are contiguous to it; and it is also mixed in some places with green carbonate of copper and with sulphate of barytes. ”

“ They seldom exceed a few inches in thickness, and are in general much more slender; the same vein which in the middle is an inch or two in thickness, gradually thins away at each extremity, sometimes to a hair's breadth, at other times shooting of like a spreading root of delicate fibres. ”

“ It is of a bluish green colour, apparently derived from chlorite, with purplish stains and including small spherical masses of a white earthy texture, which give to the mass an amiygdaloidal structure: it may be considered as a variety of argillaceous slate, and as it occurs in strata conformable with the usual varieties of the grauwacke formation, it belongs I have no doubt to the same class: it is found to be very useful as a fire stone. ”

“ The north hill which extends along the shore from Minehead to Porlock, forming a very hold and precipitous coast, affords the best opportunity of studying this grauwacke formation. At Greenaley point, about a mile westward of Minehead, there are very lofty sections where the alternations of the different varieties may be distinguished, and where there are also very good examples of these curvatures, which, in this formation, are of such frequent occurrence. ”

“ The other variety of the limestone is of a much darker colour, but is most particularly distinguished by the strong fetid smell it gives out when struck by the hammer, and when it is burning in the kilns. ”

“ Towards the exterior, madrepores are very distinctly seen, and in some of the beds the stone is full of circular bodies composed of large crystalline plates of calcareous spar, which I have little doubt are entrochi, but I did not discover a shell any of description.
§ 15. In the quarries at Great Holwell there may be seen on a small scale that occurrence of caverns so frequent in limestone. They vary in width from half a foot to five feet, and their height varies with the thickness of the beds. ”

“ Their occurrence in detached spots, and their appearance in the quarries where they are most extensively wrought, seem to point out that they are not regular strata conformable with those of the slate above and below them. Flattened spheroidal masses of the same kind of limestone are frequently found, completely enveloped by the slate, and very similar to the balls of clay-iron-stone in slate clay, but thinning away at the edges much more than those do. ”

“ In several places the surface of the limestone strata is exposed for a considerable way, shewing that in many instances they do not consist of a continuous mass, but of an accumulation of columnar distinct concretions, resembling the Giant's Causeway on the coast of Antrim. ”

“ It is always in thicker strata than the other variety and abounds in organic remains, it is also very much penetrated by pyrites in many places. These fetid strata have much less the property of setting under water, and are best adapted for agricultural purposes, for which the other are very unfit. The quarries on the spot call the first blue lyas and building lime, the other black lyas and ground lime. ”

“ The smaller twigs and branches in the brown matter, which look like the roots of underwood, also penetrate the blue clay, and the clay contains a great deal of that particular plant which appears the least decayed in the brown matter. ”

“ Similar curvatures are to be seen at Hurstone point, the western extremity of North hill. These appearances are so well known that drawings of them are unnecessary: they are very analogous to those observed by Mr. Conybeare in the same rocks on this coast, some miles westward, and represented in the 33d and 34th Plates of the 2d. Volume of the Society's Transactions.
§ 6. In every part of the district where the slaty varieties prevail, the ends of the inclined strata as they rise to the surface become either vertical or are very much twisted. ”

“ Some of them however are smooth, as if sawed across, which has probably been the case, for a great deal of the timber has been carried away by the country people; and I was told by a farmer who had lived a great many years in the neighbourhood, that he recollects when there were stems standing erect above the height of a man, with lateral branches extending from them. ”

“ It is called in the Survey the Bagborough station, being immediately above the village of that name. Doucebury I found by the barometer to be 1022 feet, and Cothelstone Lodge 1060 feet above low water mark; but as both these measurements were made under very unfavourable circumstances, they are not to be relied on. Doucebury must be considerably higher than I found it to be; the measurement of Cothelstone Lodge is probably not very far from the truth, judging in both cases from the comparison between the three heights when seen at a distance. ”

“ It is very durable when used for building, and Watchet Pier has been repaired with it. The Popple rock of Vellow extends as far as Yard farm, and I observed it in the road near Quark-hill farm on the eastern side of the brook. ”