The river Devon takes its rise in the parish of Black ford in the county of Perth, on the north side of the Ochill mountains. It runs eastward about 12 miles through the mountain glens, and then takes a sudden turn to the westward, at a place named the Crook of Devon, and keeps a western course till it falls into the Forth at the village of Cambus, immediately opposite to its source, which 's only six nines distant in a north line. This river, after leaving the mountain district, flows through broken ground and rocks, which are chiefly of greenstone. These are worn into deep dark chasms, fearful to behold, and where the water is scarcely visible. One of these chasms is named the Deil's (Devil's) Mill, from an uncommon sound produced by the water very similar to that of machinery. Below this is the Rumb ling Bridge, very narrow and without parapets, built across a narrow dark chasm, 90 feet deep ; and further down the river is the Cauldron Lynn, where the water has scooped out the rock into the form of immense caul drons, where it boils and foams without ceasing,and shews what strong effects even the attrition of water will pro duce. These objects are well worthy the attention of the naturalist, or the traveller of taste. This river, after dashing with impetuosity through rocky cliffs, at last flows placidly, in beautiful meanderings, through the pic turesque and fertile valley of the Devon, till it joins the Forth. It is rendered classic by our poet Burns, who has styled it, The clear winding Devon. Through the valley the river flows upon a bottom of gravel, the banks being of a deep sandy loam, and towards the Forth they are of a strong clay. The tide flows only about half a mile up, where ships of small burden can enter.
The Black Devon is the only other river in the coun ty. It rises amongst the Saline hills in the county of Fife, passes north of the town of Clackmannan, and dis charges itsel fhnmediately south from Clackmannan tower into the Forth. This river, from its source to its mouth, passes over strata of the independent coal formation, which is in many places exposed to view, and worthy the attention of the mineralogist. The tide only flows about a mile up this river, to a place named Parkmill.
The chief harbour and port in the county is Alloa, where there is excellent and safe accommodation for ves sels. It has a customhouse, with a full appointment of officers; and as a port, comprehends Kincardine in the county of Perth, and Stirling, besides several intervening creeks on both sides of the river. At present, (1813) there are ten thousand tons of registered shipping be longing to the port, which are daily increasing. See ALLOA.
As to the minerals of the county, the rocks which compose them belong to two classes only, viz. the tran sition, and the independent coal formation. The Ochill mountains, which are on the north side of the county, are hold on the southern aspect, deeply indented (not rugged) in their horizontal line, with winding glens. Bencleugh is the highest of the range, being 2450 feet above the level of the sea, having a long fiat summit or ridge. Dun Myat, or the Hill affair Prospect, is 1345 feet above the level of the sea, and commands a most ex tensive and delightful view. The rocks which compose these mountains are of grecnstone, flinty rock very splin try, basalt, amygdaloid, varieties of the trap class, petro silex, and very coarse breccia, which latter composes the mass of rocks upon the western part of the mountains. Veins of lime-stone are found intersecting the hill strata. Beautiful agates (Scotch pebbles) are frequently found in the loose soil of the mountains ; and also varieties of crystallized quartz, but of no value. Silver and copper have been wrought to a considerable extent in the Ochills. Lead and iron ore (hematites) have also been wrought on a small scale. Cobalt was found abundantly along with the silver, and ores of arsenic have also been occa sionally found. These mining concerns have uniformly proved unsuccessful,and arc now wholly abandoned, with considerable loss. In the veins, calcareous spar abound ed, and barytes was found in large masses. The lead was wrought at Dollar, the silver and cobalt at Alva, the iron ore at Tillycoultry, and the copper at Blair-Lo gic and Airthry. There was a salt spring in the Airth ry mines, but the kind of salt which impregnated the water was never tried. There is every reason to con clude, that these mountains abound with metallic veins. No mines or shafts have yet been driven under the level of the plain adjoining them.
The strata of the coal field extends from the foot of the Ochills along the whole of the county, and are con nected with the great coal field of Scotland. The coals found in this county arc abundant, excellent, and valua ble. The prevailing dip of the strata is to the north east. The coal field is intersected with immense slips or dislocations of the strata, which have depressed the latter in sonic instances above 200 yards, forming distinct new fields of coal. Two main slips have been ascertained, and these run somewhat in a parallel line with the Ochills. Many diagonal slips have been discovered in working the coal of considerable extent, and a great number of small ones in every direction; still, however, the Clackmannan shire coal field is reckoned a clear field in comparison with other fields. Though the general dip of the coal strata here is to the north cast, each seam of coal has a dip inwards from the wings or verges upon the line of beau nig, so that each field, taken simply in the abstract as a stratum of coal, is in its form the portion of a cup or flat bason, a form very generally found in coal fields. The Clackmannanshire coal strata keep the dip formerly mentioned, till the north field approaches the Ochill mountains, when the dip suddenly changes, and the strata rise towards the mountains, so that at their foot the va rious coal strata and coals arc found conforming to the acclivity of the mountain face, and perfectly regular.
The coal strata are cut through in many of the glens by the water, exposing to view objects highly interesting to the geologist. The junction of the coal strata with the mountain rocks is most distinctly seen at the Wester town Glen of Tillycoultry. The ()chills arc the boun dary line of the great coal field of Scotland upon the north, no coals having been found beyond them. The strata which compose this coal field arc, varieties of sand stone, reddish, white, and grey colours, some of which are excessively hard, various kinds of shale or argilla ceous sliistus, bands of ironstone, and fire clay ; green stone, from its situation, may also be reckoned amongst the coal strata ; as in one of the hill glens, it is either the lowest of the coal strata, or the first or uppermost of the mountain rocks, balls of ironstone are found abun dant in the schist or shale. In the lowest series of the strata, and upon the verges of the coal field in the line of hearing, limestone is found, which arrangement agrees with many of the coal fields in Great Britain. Organic remains are found very abundant in the strata, particu larly of the fresh water muscle in the ironstone, and of trees and plants in the sandstone, schist, and coal ; many of these are of plants which are not found growing in Great Britain, but appear to belong to the equatorial regions. There has been ascertained in the Clackman nanshire coal field a great number of scams or beds of coal, varying in thickness from an inch to nine feet, amounting in the agregate to fifty-nine feet of coal: the thinnest scam which has been wrought is twenty-seven in ches thick. All the coals arc of the open burning kind ; and in general both cubical and slate coal are found in the same bed, which, in working, turn out in large quad rangular masses. None of the Scotch smithy coals are found here, or any in quality similar to the Northumber land caking coals. Many collerics have been opened and are now carrying on here ; they arc in every parish, Lo gic excepted, which lies west of the verge of the work able coal seams. Some of these collieries have been open for two centuries, and arc wrought to a considerable ex tent, the deepest pit being about fifty-five fathoms. The collieries, as to the scale of working, stand thus: Alloa, Saucily, Clackmannan, Dollar, Kennet, Tillycoultry. The present annual output of coals may be taken at 130,000 tons, the greater part of which is exported to Leith, Taywater, and Dunbar. The noxious air common ly generated in the coal mines is carbonic acid gas, term ed chock damp; it issues continually from the fissures of the whole (heal) coal and from the strata adjoining. At tention requires to he paid to the ventilation of the pits, otherwise this gas would quickly accumulate, and pre vent the workmen entering the mine. No vestige of (in flammable air) hydrogen gas was ever seen in the coal mines till lately, when, in driving a stone mine at Old Saucily colliery, it accumulated and exploded, without producing any bad effect. The water produced in the mines is very Inird, being in general much impregnated with lime and sulphur. Ironstone is the only other mi neral wrought to any extent, which is used at the Devon iron furnace, in the parish of Clackmannan ; it is of the common argillaceous kind, and yields from 25 to 30 per cent. of iron. Freestone is found in abundance, but none of it is remarkably fine either in colour or quality. Large blocks of greenstone are found thinly scattered over the surface of the county ; but as no rock mass of that kind is found nearer than six miles to the westward, many theories have been given by philosophers, as to the natural means by which they have been transported from their original rock. The great mass of grecnstone rock in this county is Abbey Craig near Stirling; it is bold, rug ged, and precipitous towards the south-west, and slopes or dips to the north-east, having no superincumbent rock strata. The bottom or the precipice is covered with huge blocks of this rock, which in former ages must have fall en down. This rock, in its general structure, is rudely columnar, above NO feet thick, and rests upon the com mon alternating series of coal strata, composed of sand stone, shale, and coarse limestone, mixed with iron. In this last, petrified shells are abundant. The surface slope of this immense rock seems to conform with the dip of the strata on which it rests, a point in the mineral field, worthy of the attention of the geologist. This rock, in its fracture, is found both of an open and close grain, and of crystallised appearance, composed of feld spar and hornblende, with minute crystals of pyrites. It is difficult to break under the hamMer. It is tough ra ther than splintery. It dresses with a regular face, simi lar to the Aberdeen granite; but its particles are much more cohesive than the granite; this superior quality in duced an ingenious miller, of the name of Brownhill, to try this rock as a substitute for French burstones in the manufacture of flour, as the burstones, on account of the war, had become very high in price ; he succeeded be yond his expectation. And so much are these millstones approved of, that they arc in general request both for flour mills and distilleries for gristing. They are built in pieces, similar to the burstones ; are uniform it, the cut ting surface, and dress well, a quality deficient in the burstones. As a proof of their utility, above 300 pairs of these millstones are now used in Scotland and England. They sell at from sixteen to twenty guineas a pair, where as bursto»es cost about sixty guineas ; hence an import ant acquisition is made, and also a great saving of expcnce. The Society for the encouragement of Arts presented Brownhill with one hundred guineas for the discovery.