Felsite with mica-aggregates. Exminster. Granular greyish-drab felsite, with acicular schorl. Exminster. Fine-grained reddish felsite, with porphyritic quartz and felspar, base sprinkled with black specks. Exminster. Red felspar and schorl-rock. Exminster. Quartzo-felspathic rock with blebs of quartz, large porphyritic felspars, and schorl. Teignmouth. Base black schorl and quartz, with porphyritic quartz and felspars (kaolinized); a little mica. Teignmouth. Porphyritic vein-stone, with Murchisonite, decayed felspars and schorl. Exminster. (Possibly associated with andesite.) Fine-grained grey felsitic rock, with quartz-blebs, porphyritic felspars, kaolinized felspar-granules, fine mica, and acicular schorl. Exminster. Grey granular felsite, with quartz, mica, and schorl. Exminster. Schorlaceous felsite. Red compact base with small porphyritic felspars, quartz-blebs, mica, and patches of blue radiating schorl. Teignmouth. Reddish felsite with dots and nests of schorl, bluish-grey and radiating, radial structure also in ground-mass. Teignmouth. Schorlaceous felstone, with more prominent porphyritic felspars, nests of schorl-needles, and some porphyritic quartz. Teignmouth. Schorlaceous felsite ranging from fairly compact to granular; long felspar-crystals, quartz-blebs, decayed mica-clusters, light spotty schorl. Teignmouth. Rock with an andesitic rather than a felsitic look, but containing occasional needles of schorl. Teignmouth. Slightly amygdaloidal andesite, granular base with quartz-blebs and porphyritic felspars. Suggests felsitic alliances, and present aspect may be in part due to alteration. Exminster. Speckled variety, with blackish patches. Felted andesitic porphyry, red-speckled, lined with white. Heavitree. Schorl rock. Teignmouth, Exminster, Heavitree-almost universally distributed. Schorl-vein-stones, some laminated. Exminster. Felted schorl-rock, with porphyritic felspar. Exminster. To the foregoing may be added the description of a few Cornish granites and elvans, some because they are on the borders of the two counties and therefore can hardly be excluded from survey; others for special purposes of comparison. The Withnoe example, for instance, has most important bearing on the general question of origin and structure. Gunnislake. Grey: irregular-textured granite, felspar largely predominating, white mica. Gunnislake. Light greenish-grey: a somewhat open-textured greisen with gilbertite. Mount Edgcumbe (exact locality unknown).-Red: apparently a syenitic vein, mainly reddish felspar, with a little quartz and a small but marked proportion of hornblende. Luxulyan. In this locality were raised not only the well-known luxulyanite of which the Duke of Wellington's sarcophagus is made, but the magnificent porphyritic felsites with which Mr. Treffry built the "porphyry hall" at Place, Fowey. Among some of the most characteristic of these are a variety with a rich redbrown base thickly sprinkled with small cream-coloured felspar crystals and quartz blebs; a luxulyanite in which the felspar is red instead of pink; and pink, red, and drab porphyritic felsites in general structure resembling the brown, but with the addition of schorl. The best idea of the variety of the granites and felsites of this part of Cornwall will be gained by a visit to the "porphyry hall," or an examination of the inlaid table in the mineral grotto at Menabilly, near Par. St. Just.-There is a very remarkable variety of granitic rocks in the St. Just district, for examples of which I was indebted some years since to my lamented friend the late Mr. T. Cornish, of Penzance, a man of science of whom his birth-place-Tavistock -may well be proud. They mostly came from St. Just United. The specimens include: luxulyanite-pink felspar, black schorl, and quartz; a coarse grained granite, with olive-grey felspars, very prominent nests and plates of black mica and a little quartz; a coarse variety of luxulyanite, in which the felspar is thickly charged with schorl; a chloritic granite sprinkled with beautiful crystals of deep purple fluor, containing also a little chalcopyrite and iron oxide; and another fluoriferous rock, consisting almost wholly of pink crystalline felspar, scaly granular mica, and brilliant fluor crystals. South Caradon.-Dull light green coarse-textured granite, pale orange felspars, white mica, and an abundance of chlorite-a well-marked chloritic granite. South Caradon.-Bright green: an irregular textured granite, with pinkish felspars, in which the quartz and felspars appear charged with copper. South Caradon.-Red and grey: a coarse semi-crystalline granite with dark red, mainly decayed, felspars; the bulk of the rest of the rock is mica, granular and in part platy. South Caradon.-Light brown: a felsite with a generally developed imperfectly crystallised matrix. Wild Duck (Redruth).-Creamy-grey this is a well known building elvan in Cornwall, with granular texture, easily mistaken on a casual glance for a sandstone or an oolite; which an elvan at Newham near Truro, has frequently been. Scilly.-Deep red mainly composed of felspar with micaceous strings and patches and acicular cavities. St. Stephens.-Light cream colour: chiefly quartz and kaolinized felspar with a general granular structure, associated with gilberlite-the china stone of Cornwall. Withnoe. This is a small detached exposure of the andesite of Cawsand Bay, which was always included in Devonshire until recent legislation transferred it to Cornwall. Scientific research can, however, hardly be expected to be bound by purely legislative convenience; and the phenomena presented by this rock have a very important bearing upon the question in hand. The chief feature here is the occurrence of a slightly porphyritic Indian-red pitchstone (including felspar, occasionally in imperfect crystals, a little quartz in blebs, black mica in flecks and occasional crystalline plates) with distinct flow structure, which in the space of ten or a dozen feet passes by devitrification and increased porphyrization into a light-grey rough open-textured trachytic felsite-in parts more than half crystalline; with abundant black mica, quartz in large corroded blebs and grains showing occasional approach to crystalline form, felspar strongly developed with good crystals numerous, several twinned after the ordinary local granitic type. The volcanic origin is clear, and yet this is essentially an ordinary variety of quartz-felsite or elvan. POSTSCRIPT. Erme Mouth, coves east of. I am indebted to Mr. W. A. E. Ussher, F.G.S., for calling my attention to the granitic and porphyritic pebbles on the beaches east of Erme Mouth, where they are very plentiful. All noted either absolutely identical with or akin to Dartmoor types, with some rather exceptional forms. They are chiefly felsitic rather than granitic, with several examples of the schorlaceous varieties. The leading varieties include: Red-brown felsite with vitreous matrix developing imperfect crystals of dark-red felspar, and blebs of quartz; schorl in flecks and patches. Dull pinkish-brown felsite, with sub-vitreous matrix developing small porphyritic felspars and quartz-some of the former well crystallized; schorl fairly disseminated. Dull red felsite, with sub-vitreous matrix, and irregular development of felspar and quartz; fairly disseminated schorl; some of the felspars show twinning. Pinkish-red pegmatite with patches of schorl; crystalline-granular texture; felspar dull and partly kaolinised. In another example the base is mainly felspar of a more massive kind; and the schorl is less frequent, in small rounded radiates. Yellowish-red pegmatite, some of the quartz blebs yellowish, somewhat earthy matrix; there are several varieties of this rock, one a distinct orange. Pinkish felsite, finely-granular earthy base with porphyritic felspars and quartz blebs, and small circular nests of schorl. Cream-white felsite with compact sub-granular base (conchoidal fracture) enclosing small imperfectly developed felspar crystals, quartz granules and schorl needles, Very finely-granular schorlaceous pegmatite, light red, evidently once a fine-grained granite, of a type which also occurs, containing in addition to the schorl a little black mica, and some porphyritic quartz and felspar. Light red schorlaceous granite, granular texture with a few porphy ritic felspars; some of the matrix felspars bright red. Irregular textured and veined schorlaceous pegmatite, pale red. Well-charactered pegmatite, chiefly granular, with a few porphyritic felspars, some twinned, and quartz masses. Smaller felspar crystals bright red, contrasting strongly with the schorl; some of the larger felspars zoned with red-a very pretty rock. Warm-brown porphyritic granite, glassy-granular matrix, black mica. Coarse-textured schorlaceous granite, verging on greisen, abundance of white mica, felspathic matter kaolinised; another example is distinctly a griesen, in part. There are various examples of schorlite, two containing porphyritic felspars, and a highly altered junction rock-a granular gneissose micaceous schist with development of schorl along the original lines of bedding. A CHAPTER IN DEVONSHIRE HISTORY: COUNTY DEFENCE IN 1794-97. BY P. F. S. AMERY. (Read at Plymouth, July, 1892.) I AM indebted to Lord Clifford for the perusal of documents in his possession at Ugbrooke relating to the measures taken to place the county of Devon in a state of defence in 1794-7. The records consist of the minutes and correspondence of the County Defence Committee, of which Lord Clifford's great-grandfather was the chairman, and they appear to have been finally deposited at Ugbrooke when the committee dissolved in 1797 or was superseded in 1798. To fully understand the gravity of the occasion we must in some measure realise the state of England in 1794. Mr. A. H. A. Hamilton, in a lecture on "Devonshire Volunteers," referring to that date, remarks: "The effect of the French Revolution was felt here. As early as 1792 elaborate plots were formed to supersede Parliament by a National Convention after the French model, and to abolish the monarchy. It was found necessary to suspend the Habeas Corpus Act. Great distress prevailed in the country. The rate of interest rose to 17 per cent. At the same time the prospect of invasion was always imminent. As early as 1793, Monge, the French Minister of Marine, threatened to make a descent on England with 50,000 caps of liberty, and to overthrow the Government of the country. Toulon, which we had assisted to garrison (and the Devonshire Regiment, it may be remarked, formed a part of the contingent), was forced to be evacuated." |