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in are speedily suffocated; and it takes its name from the dogs which are placed in it by way of experiment. The cave and its neighbourhood appear to have undergone
some considerable changes; for, from Pliny's reference to the mephitic gas, it would seem to have been fatal to human life, which is not possible now, owing to the small height of the stratum, unless an individual threw himself upon the surface of the floor. According to some ancient accounts, bubbles were constant upon the lake Agnano close by, occasioned by the escape of gas, of which there is no appearance now; so that the quantity of deadly air exhaled has been much reduced, if dependence may be placed upon these authorities. A similar instance, on a much larger scale, is seen in the crater of the extinct volcano of St. Leger, or of Neyruc in the south of France, on the banks of the Ardêche, amid the great number of volcanic remains of that region. This crater exhibits a cultivated, and in part inhabited, district, which is surrounded like an amphitheatre by the ancient walls of volcanic débris. Its soil is one vast sieve for the ascent of carbonic acid. Perforations have been made in it to facilitate the emission of the gas, and guide it from the fields, to which its contact is very injurious. The height of the bed of gas, over the ground of these holes, has been found to be, in the most favourable circumstances, about one foot and a half. Changes of weather have the most important influence on it; and in violent rains the whole mass of gas is absorbed. The quantity of this gas, which issues from the soil of the whole neighbourhood, has a very striking influence on the health of the inhabitants who work in these fields; and if the proprietors do not yearly clear out these perforations, their harvest is lost by means of the poisonous vapours. Another example occurs near Pyrmont, where there is a cavern of mephitic gas, named Dunsthohle, which exhibits the same phenomena as the dog grotto near Naples; and of a kindred kind is the extraordinary valley in the island of Java, called by the natives Guwo-upas, poisoned valley, which is without vegetation, and strewed with the skeletons of human beings, quadrupeds, and birds, being generally half-filled with a noxious gas which destroys life in a few minutes.
In addition to the cavities which are the handiwork of nature, immense subterranean
spaces have been excavated by the labour of man, chiefly in the limestone, coal, and salt formations, to obtain the products which are essential to the arts of life. At certain points and limits of the South Staffordshire "Coal Basin," the limestone stratification is abruptly exalted from its normal position, which is several hundred feet below the regular surface, and forms a striking object in scenery, and a picturesque mountain boundary, to the district of towns, hamlets, and villages, in which the usual mining operations for coal and iron stone are pursued. It is worked to procure a valuable flux for the iron furnaces -cement for building-and a manure for agricultural purposes. Dudley Castle Hill is
Caverns of Dudley Castle.
a bold and rugged prominence, where the quarries were primarily worked. The excavations at first were open to the light, commencing from the protruding ridges and peaks, and forming in time a deep hollow or ravine. Clearing the rock as far as was convenient, the rapid inclination of the stratum was followed, and the work was then continued at a much lower level, in the form of gloomy tunnels, afterwards threaded by dark and dangerous canals, necessary for the conveyance of the product of the perforated region. At the lower part of the castle grounds, and not far distant from the Eastern Lodge, is the descent to one of the great caverns, answering to our illustration. By a few uncertain slippery steps the visitor arrives at the moist crumbled floor of a wondrous avenue of rock works. Indistinctly, and at an inferior plane, glimmer the dull waters of the canal, the line of which is only broken in part by a covered way, to re-appear in the onward distance of the hazy mine. As the strata are sometimes at an angle of eighty degrees, sometimes less, the enormous broad-footed pillars of material left to support the irregular roof, answer to such inclination, and are perpendicular to it, presenting a wild and singular appearance. The force and sublimity of this scenery by torchlight are most interesting, and the frowning boundaries of the spacious crypts, the pillars, and the rude chambers, remind one distinctly of the mazes of the Memphic tombs. Proceeding to the left,
and near to the porch of the cavern delineated, as also in progress towards the other extremity, yawning apertures aloft and laterally communicate with the celebrated ravine in the castle bounds, and receive a blue misty light into the gigantic casemate which illuminates the glistening and sparry walls, displaying the white frosted vapour upon the lips of the attendants and their guide. In sultry weather much danger is incurred by entering the caverns insufficiently protected from an altered temperature.
The demand for the mineral treasures of the earth, and especially its coal, created by the advance of civilisation, has caused the undermining of its surface upon an extraordinary scale in modern times, though some of our own mines date their origin from the era of the ancient Britons. This is the case, as the name imports, with Odin's mine, at the southern foot of Mam Tor in Derbyshire, a place deserving a visit. A shaft, nearly
a mile in length, leads to the vein of ore that is now worked, which varies in thickness from two or three inches to as many feet. Beautiful crystallisations of blende, barytes, calcareous spar, and selenite are found in this extensive excavation, as well as the curious and dangerous mineral called slikensides. "The effects of this extraordinary mineral," says Mr. Rhodes, "are not less singular than terrific. A blow with a hammer, a stroke or a scratch with a miner's pick, are sufficient to rend those rocks asunder with which it is united or embodied. The stroke is immediately succeeded by a crackling noise, which is sometimes accompanied with a sound not unlike the mingled hum of a swarm of bees; shortly afterwards an explosion follows, so loud and appalling that even the miners, though a hardy race of men and little accustomed to fear, turn pale and tremble at the shock. This dangerous combination of matter must consequently be approached with caution. To avoid the use of the common implements of mining, a small hole, is carefully bored, into which a little gunpowder is put and exploded with a match, which gives the workmen time to withdraw to a place of safety, there to await the result of their operations. Sometimes not less than five or six successive explosions ensue at intervals of from two to ten or fifteen minutes; and occasionally they are so sublimely awful that the earth has been violently shaken to the surface by the concussion, even when the discharge has taken place at the depth of more than one hundred fathoms."
ATER, essential to the existence of man and the fertility of the soil, occurs in each of the physical conditions which bodies are capable of assuming the gaseous, solid, and liquid states. In the form of vapour, sustained in the atmosphere, it will be treated of in another section. In the solid condition, one of its aspects has been previously referred to- that of the glaciers of high mountain regions; and in the lowland districts of the temperate zones, water annually assumes a solid form, a mantle of snow lying upon the ground in winter, and a coating of ice upon the pools and rivers. Upon high elevations, also, even within the tropics, these phenomena are perpetual; and, upon the level surface of circumpolar countries, snow and ice are constant features of the landscape. In a liquid state, the continental waters have the character of springs, rivers, or lakes, which vary greatly in their external appearance, and in the chemical composition of the fluid. The oceanic waters likewise display these characters; for we may regard the broad expanse of different seas as vast lakes, while the numerous, strong, and permanent currents that occur are the rivers of the deep; and in various places it is certain that jets of fresh-water rise from the bottom of the ocean, which materially lessen its saltness in their neighbourhood. In the Gulf of Spezzia, a branch of the Gulf of Genoa-one of the finest harbours in the world, and of exquisite beauty-there is a powerful jet of fresh water rising in a liquid column from the bed of the sea; and on the south coast of Cuba, at a considerable distance from the shore, there are fresh-water jets of such force, that boats cannot approach them without hazard. The general division of the waters of the globe is into salt, mineral, and fresh water. The ocean is the grand example of the former; but there are many continental specimens of saline springs and lakes, which proceed from combination with rock-salt or sulphate of magnesia. The mineral waters arise from sulphur, arseniates, or other metallic substances, derived from the circumjacent earth, held in solution. For the most part, however, the continental waters are fresh, or somewhat similar to distilled water, whether resulting from rain, or the melting of snow and ice, and constituting either springs, rivers, or lakes.
Springs, whether gushing rapidly from rocky clefts, or gently oozing out of banks of earth, are interesting objects in the landscape, from the general purity of their waters, the frequent seclusion of their situations, their murmuring flow, and the green enamel of mosses and flowering plants to which the refreshing virtues of their streams give birth. There are not a few springs whose history may be traced back thousands of years, and which have acquired celebrity from their association with events and personages of a far remote antiquity. Who has not heard of the fountain of Arethusa, with its dark water, to which the hero of the Odyssey was directed by the goddess, upon returning to his native Ithaca?
"Go, first the master of thy herds to find,
At the Coracian rock,
Where Arethusa's sable water glides."
tain is about
six miles in the interior of the island, the road ascending all the way. It is a small basin at the top of a ravine, and is
percolations through the superincumbent rock.
Seated on a
broken arch before it, the
sides of the
glen appear clothed with
leafy plants and odoriferous shrubs; and onwards
are seen scattered on all sides, but are becoming effaced." Who also has not heard of the fountain of Castalia, in which the Delphian Pythoness laved her limbs, and from which she, and the poets who versified her answers, were believed in part to derive their inspiration? The poetical expression, the "dew of Castalie," refers to the spray of a cascade which descends through a cleft of Parnassus, fed by the snows upon its summit; but the fount of inspiration, the bath used by the Pythia, is supposed to be a small shallow basin on the margin of the rill of the cascade, supplied with its own perennial stream, which unites its superabundant water with that of the adjacent stream. Here