X. Obserrations on the specimens of Hippurites from Si

cily, presented to the Geological Society, by the Hor. Henry Grey Bennet. By James Parkinson. The Hippurite belongs to the class of multilocular shells, which appear from the numerous remains of Cornua Ammonis, Orthoceræ, Belemnites, &c., to have been socommon in a former state of the world. The few Nautili which we possess at present, throw but an imperfect light upon the structure of these animals. Mr. P. prosecutes in this paper, a subject which he had taken up in his work on Organic Remains ; and endeavours to discover the disposition of the inhabitant, from the arrangements of his long forsaken house. The principal point ascertained, is, the power of change of place, by altering the relative buoyancy of the shell, and thus rising to the surface, or sinking to the bottom of the sea.

XI. An Account of the Coalfield at Bradford, near Man

chester. By Robert Bakewell. Communicated by Dr. Roget.

This is a small coalfield resting on a red sandstone, probably a variety of the Derbyshire and Yorkshire millstone grit. One of the beds on its northern edge, instead of dipping thirty degrees S. the regular inclination of the strata, rises to the surface perpendicularly, and has been worked in this direction to the depth of forty feet.

XII. Some Account of the Island of Teneriffe.

By the Hon. Henry Grey Bennet. The Peak of Teneriffe, towering in peerless majesty from the expanse of the Atlantic to an elevation of twelve thousand five hundred feet; the cloud capped landmark-once, the flaming beacon of an horizon ninety leagues in diameter; is an object as attractive in description to the imagination of the reader, as it is in nature to the eye of the navigator. For a traveller to ascend its summit, and speak plain, simple truth when he gets to the bottom again, would seem almost to imply either a total want of ability to embellish, or uncommon reliance on the native charms of veracity. Mr. B. endeavours simply to convey correct ideas of the matter, form, and magnitude, of the objects he visited ; yet we are greatly mistaken, if a poetic imagination will not build a more beautiful superstructure upon these materials, than on the descriptions of such as endeavour to excite in their readers, sensations--the effects of the scenes they beheld, by sounding epithets and splendour of diction. Those who have no poetry in their souls, will, we dare assert, lose nothing on this score ; and, at any rate, they will obtain interesting geological and geographical information.'

The whole of the island is evidently of volcanic origin, the lowest stratym being a bed of porphyritic lava covered by scoria and pumice. Upon this rests a bed of Rocca verde, or greenstone, composed of felspar and hornblende, on which generally lies a thick bed of pumice. And, lastly, towards the surface, are basaltic lava and asb. In some places, more than one hundred strata of lava appear above each other; and these at times individually attain a thickness of a hundred or a hundred and fifty feet. 'l'he number of small extinct volcanoes, is prodigious; and the streams of lava, which have flowed from them, are beyond enumeration.

Mr. B. ascended the Peak, from the town of Orotava, on the 16th of September, 1810. After quitting the cultivated part of the acclivity, he traversed a forest of chesnut trees of large size, mixed with shrubs of the erica arborea, eighteen or twenty feet high : he then rode for two hours over a succession of green hills, whose vegetation, dwindling by degrees, was at last reduced to the Spanish broom.

• Leaving behind us this range of green hills, the track still ascending, leads for several hours across a steep and difficult mass of lava rock, broken here and there into strange and fantastic forms, worn into deep ravines, and scansily covered in places by a thin layer of yellow pumice. The surface of the country for miles and miles around, is one continuous stream of lava; the rents or ravines of which seem to be formed partly by the torrents from the hills flowing for so many ages, and partly from that tendency, characteristic of a lava current, to keep itself up in embankments, and, in its cooling process, to open out into those hollows which I have uniformly observed in every eruption of lava that I have had an opportunity of examining...... At length, an immense undulated plain spreads itself like a fan on all sides, nearly as far as the eye can reach ; and this plain is bounded on the west south west, and south south west, by the regions of the peak, and on the east and north east, by a range of steep perpendicu, lar precipices and mountains, many leagues in circus ference called, by the Spaniards, Liis Faldas, which evidently formed the side of an immense crater. This tract, according to the authority of M Escolar, contains 12 square leagues from which perhaps originally the lavas of the isle flowed, which might have thrown up the cone of the peak, and covered the wide spreading plains with the deep bed of ashes and pumice.' pp. 292—294.

After crossing the plain, and a torrent of lava which has flowed from the higher parts of the Peak, Mr. B. arrived at

the rocks, La Estancia di los Ingleses, where he was to take up his quarters for the night, on a sailcloth beside a fire of the dry branches of the Spanish broom.

• 1, however, passed the best part of the night,' he says, ' by the fire, the weather being piercing cold ; the view all around me was wild and terrific, the moon rose about ten at night, and though in her third quarter, gave sufficient light to shew the waste and wilderness by which we were surrounded : the peak and the upper regions which we had yet to ascend, towered awfully above our heads, while below, the mountains that had appeared of such a height in the morning, and had cost us a day's labour to climb, lay stretched as plains at our feet ; from the uncommon rarity of the atmosphere, the whole vault of heaven appeared studded with innumerable stars, while the valleys of Orotava .were hidden from our view by a thin veil of light fleecy clouds, that floated far beneath the elevated spot we had chosen for our resting place; the solemn stillness of the night was only interrupted by the crackling of the fire round which we stood, and by the whistling of the wind, which, coming in hollow gusts from the mountain, resembled the roar of distant cannon.' p. 296.

From this place our travellers proceeded on foot, climbing precipices of lava, and acclivities of loose pumice, till they arrived at that division of the mountain, called el Mal Paris ; an immense mass of lava about two miles in breadth, and not less than sixty or a hundred feet deep. It does not appear ever to have been in a state of perfect fusion, the traces of vitrification being very rare. At La Cueva, they explored one of the caves common on the sides of the mountain. It contained snow, and a pool of water thirty or forty feet in depth. The roof and sides are formed of stalactitical lava. Here they viewed the splendid spectacle of sunrise.

' At first there appeared a bright streak of red on the horizon, which gradually spread itself, lighting up the heaven by degrees, and growing brighter and brighter, till at last the sun burst forth from the bed of the ocean gilding as it rose the mountains of Teneriffe, and those of the Great Canary; in a short time the whole country to the eastward, lay spread out as å map, the Great Canary was easily to be distinguished, and its rugged and mountainous character became visible to the naked eye.'

p. 298.

Near this spot commences the third division or cone of the mountain, properly termed the Peak of Teneriffe. The ascent, owing to the excessive steepness, and looseness of the pumice, is fatiguing, but it does not extend far. The top does not appear to contain more than an acre and a half in superficies, and from the highest ridge to the bottom of the

crater, there is a gradual descent of about two hundred feet. The whole summit consists of lava in a state of rapid decomposition from the sulphureous vapours which are continually exhaling, and

which deposite considerable quantities of very pure sulphur. The heat in some places is considerable, and the ground, on being struck with the foot, gives a hollow sound. The circumference of the cone, Mr. B. estimates at three miles : and the view from the summit is stupendous, so that the idea of extreme beight is more determinate and precise, than even on the mountains of Switzerland.

Mr. B. thinks the difficulties of the ascent, as described by other travellers, much exaggerated; and he encourages those who may be disposed to try it after him, with the consoling information, that there is, perhaps, no mountain in Europe, the ascent of which does not present more difficulties than the Peak of Tenerifle.

XIII. On the Junction of Trap and Sandstone, at Stirling

Castle. By J. Mac Culloch. In cutting a road, the line of junction of the sandstone and super-incumbent grunstein stratum was laid bare. In one place, the sandstone stratum was split in the direction of its stratification, the upper portion separated, bent upwards, the end irregularly fractured, and, in this condition, involved, supported, and covered by the grunstein. The difficulty of accounting for the phenomenon, on the Wernerian hypothesis, is, that it is obvious both strata are depositions by precipitation from quiescent fluids. The Huttonian certainly affords an easy solution, by supposing the agency of fire. But, as Dr. Mac Culloch remarks, Whether this hypothesis be esteemed well • founded or not, it must rest on a much wider basis than that of the mere phenomena which accompany the trap rocks.' Phenomena like that which is here so ably described and delineated, lead, however, to the conclusion--that no hypothesis is competent to explain geological phenomena at large, which does not admit of the forcible displacement of the strata which accompany them, and on which the marks of violence are so evidently impressed.

XIV. On the Economy of the Mines of Cornwall and Devon,

By J. Taylor. In almost every country in the world, England excepted, the mistaken political maxim has been adopted, that, if individuals can work a mine with profit, it must be profitable for the goEvernment of the country to work it. The British government

appears to have discovered, that the productive returns to individuals, are the creation of so much additional property to the state, while their unproductive expenditure distributes the wealth of the adventurers in supporting the indigent and industrious, without impoverishing the public coffers.

Satisfied therefore with defending private rights in the searchi after the mineral riches of the country, and with ensuring their enjoyment when obtained, it leaves the economical regulations of the mine, to the prudence of those who are most immediately interested in their efficacy. Upon the same principle, the adventurers unite their interest with that of the workinen; and the system of the Cornish mines, though defective in some particulars, is as much superior in theory to those of most other mining districts, as in the effects produced.

Mr. Taylor considers their economy, under five general heads. 1. The nature of the agreements between the owner of the soil and the Mine-adventurers. 2. The arrangements between the adventurers among themselves. 3. The mode of employing and paying the miners and workmen. 4. The purchase of materials for carrying on the undertaking. 5. The sale of Oreg to the Smelting Companies.

The first and the fourth of these, lie open to the greatest objections, as the dues, or portion of produce, either in ore or by composition, to the Lord of the soil, being disproportionately large in comparison with the damage done, discourage adventure ; and as the supply of materials is generally in the hands of Shareholders in the concern, it is their interest to encourage the prosecution of enterprises which may be ruinous to their copartuers.

The arrangements between the adventurers are simple. The accounts are examined every three or two months : in large undertakings the financial concern is intrusted to a purser; the management of the works to the captains, a class of men whose abilities and obliging attentions to such as have had occasion to apply to them for information and assistance, will be remembered with esteem and respect by all who have visited the - county on scientific pursuits. Those who 'superintend the operations of the miners, are styled under-ground cuptains, while those who direct the dressing and sorting of the ore, are called grass captains, certainly by a misnomer, as their domains, though occupied by great mineral riches, often do not contain a trace of vegetable life.

The chief excellency of the regulation of the Cornish mines, arises from the manner of contracting with the workmen, or setting the work, which is done by a species of public auction, termed a survey, at which the captains retain the right, Vol. III. N. S.


« ForrigeFortsett »