Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/158

 counties of Devon and Dorset. These eastern streams are comparatively slow and still-flowing. The Dartmoor rivers, rapid, dashing, and rocky, are famous streams. None have courses of any great length.

The formations of Devonshire are of course the main cause of the general appearance of the county. Dartmoor, as has been said, is a region. By far the greater part of central Devon is occupied by, consisting chiefly of s, often , and of s. All this formation has been subjected to great disturbances, and the strata (as may be seen on every part of the coast between and the mouth of the ), are twisted in a manner which defies description, the result being some very extraordinary and picturesque cliff scenery. does not exist, but occurs near. These rocks are also associated with pean and other es, which bear a striking analogy to those of existing es. Underlying the carbonaceous deposits are the or Devonian rocks, forming the extreme north of the county, and great part of the. They extend west of, and cover the greater part of. These rocks are generally held to be the equivalents of the &ldquo;&thinsp;Old Red&rdquo; system, although the characteristic Old Red rocks, so largely developed in, , and elsewhere, are not found at all in Devonshire. The Devonian rocks consist of -s, grey s, brown s, and s. The s of the two series also differ&thinsp;; but although these Devonians offer many complexities, this and other differences seem capable of explanation. The third great formation of Devonshire is the New Red, which occupies much of the eastern portion of the county, extends along the coast from to, and sends out a long spur westward into the Carboniferous district. The upper beds of the series consist principally of s, the middle of sandstones, and the lower of s or coarse conglomerates, coloured red by of. The formation is characterized by a scarcity of organic remains, and by the extreme fertility of some of its soils. At or near the junction of the Carboniferous and New Red formations, from, near, on the N. to on the S., occur numerous masses of , s. These traps are for the most part excellent building stones, and many of the  have been worked for ages. s and s are also associated with the Devonian series. Greensand strata cap the Blackdown hills, and the heights near, , and , and, with beds of , occupy a depression in the coast at (near the eastern border of Devonshire), coming down to the level of the sea at Beer Head. A very interesting and remarkable deposit, belonging to the  period, occurs at, below the eastern escarpment of Dartmoor. It consists of beds of, , and , with an aggregate thickness of more than 100 feet. In the lignites at least 50 species of have been found, all indicating a sub-tropical climate&thinsp;; but the greater part of the lignite beds is formed by fragments of an enormous ous tree, belonging to the , the only living species of which are to be found in. Great lumps of d occur occasionally. The clay which overlies the lignites is of much more modern date, and contains leaves of the, now an plant, and of 3  of  which all betoken a much colder climate than that of Devonshire at present. Fine occurs above this &ldquo;&thinsp;head&rdquo; of coarse clay and sand, and has been turned to account. The lignite called &ldquo;&thinsp;Boveycoal&rdquo; burns with a disagreeable smell, and is not much used.

The caverns of Devonshire are famous in. The most important is Kent's Hole, near, which has been carefully explored, and appears to have been frequented by s, s, and, at last, by primitive man. There are others at, at , and at near.

Minerals.—The of most account are  and. occurs, but to no great extent. The - at  on the N. coast, and at Beer Alston, on the Devonshire side of the, were formerly worked to advantage&thinsp;; but the former have long been abandoned, and the latter, since 1860, have been ed by water from the river, under the bed of which the principal mine extended.  has been found on Dartmoor (in stream works) from an unknown period.  was not much worked before the end of the last century. Tin occurs in the granite of Dartmoor, and along its borders, but rather where the Devonian than where the Carboniferous rocks border the granite. It is found most plentifully in the district which surrounds, which, for tin and other ores, is in effect the great district of the county. Here, about 4 miles from Tavistock, are the Devon Great Consols mines, which from 1843 to 1871 were among the richest copper mines in the world, and by far the largest and most profitable in the kingdom. The divided s during this period amounted to 1,192,960. But the mining interests of Devonshire are affected by the same causes, and in the same way, as those of Cornwall. The quantity of ore has greatly diminished, and the cost of raising it from the deep mines prevents competition with foreign markets. In many mines tin underlies the general depth of the copper, and is worked when the latter has been exhausted. The metalliferous character of the Tavistock district is indeed very mixed, and besides tin and copper, ores of ' and ' are largely distributed, but these have as yet received no great attention. At the Devon Great Consols more than 2000 tons of refined  are annually produced by elimination from the iron s contained in the various lodes. This amount is calculated to be about one-third of the arsenic produced throughout.  occurs in the neighbourhood of, in the valley of the Teign, and in N. Devon&thinsp;; but the most profitable mines, which are shallow, are, like those of tin and copper, in the Tavistock district. The other mineral productions of the county consist of s, building-stones, s, and. s occur in the Carboniferous series at and elsewhere, but of very inferior character and beauty to those among the Devonian rocks, at,  near , and. These are largely worked, and are used extensively in the decoration of es and other buildings. Among  stones, the granite of Dartmoor holds the foremost place. It is much quarried near, near on the N. of Dartmoor, and elsewhere. The annual export is considerable. There are very large and ancient quarries of a chalky greensand at, near the eastern border of the county. This is an excellent building-stone, nearly white, and composed of of lime, mixed with  and  matter, and with particles of green  of iron. Hard traps, which occur in many places, are also much used, as are the s of and of. The stone, used from an early period in Devonshire churches, is found near Tavistock, and is a hard, porphyritic, taking a fine polish. Excellent roofing s occur in the Devonian series round the S. part of Dartmoor. The chief quarries are near 