two acres of ground, whose desolation forms a very striking contrast to the verdure on nearly three sides of it. This spot is perfectly barren, and is filled up with low hillocks of friable rocks, loose stones, and débris, having the character of a moraine; it is interspersed at irregular intervals with shallow pits or depressions containing mud and sand, and sometimes foul muddy water. From cracks and fissures in these depressions arose clouds of steam; and yellow patches of sulphur were visible from a distance.

At the time of my visit, in the middle of June 1866, there were seven or eight springs in a more or less active condition, from which clouds of superheated steam arose, either by a small round hole or narrow fissure, or by several such apertures. The rushing steam produced a loud noise, like that accompanying the blowing off of steam from a boiler; and above the fissures was a quantity of sublimated sulphur, adhering to the rock in acicular crystals, forming, about the most active spring, a bright-yellow patch which was visible from a considerable distance. It was no easy matter to reach the sublimed sulphur; for, on a close approach to the spot, a jet of hot steam made it necessary to withdraw, and warned us that a nearer approach was dangerous. I managed however, with the aid of a stick, to procure some from the crevices, on and around which it was deposited. Most of the springs were dry; but one rose through muddy water, which bubbled up in a series of rapid explosions, carrying the boiling water, sand, and mud 5 or 6 fect high, and splashing it all around.

It is evident that the degree of activity of these springs is very variable, and that at the time of my visit they were in a comparatively quiescent state. The jets of steam were isolated, and a comparatively small portion of the two acres at which I estimated the area of grey barrenness was in an active condition. Numerous pits, which had evidently at some period sent forth their jets of steam, were perfectly quiet and stones coated with sulphur scattered among them showed their occasional activity. Moreover the edge of the level, where it began to descend down the ravine before mentioned, was covered with a thick crust, which had evidently been at one time in a semifluid state, and had slowly flowed, a viscous mass, over the edge, and now had the appearance of dried asphalt. This was doubtless the remains of mud through which the sulphur rose, such as we saw in some comparatively small pools, but which at one time had been in sufficient quantity to rise above the general depression and run over the edge into the ravine.

The sulphur appeared in all cases to be deposited in a perfectly pure sublimed form; nor was there any smell to be detected in the active springs themselves. The steam is laden with the element in a dissolved condition, and deposits it in pure crystals upon any substance with which it comes in contact. The effects produced upon the calcareous rocks were in all cases due to the disintegrating and bleaching power of steam; and the smell of sulphuretted hydrogen was most perceptible in a spot where the rocks had been disintegrated, but where there was no sign of present activity.

It has been supposed that the locality is very fatal to animal life, from the presence of sulphurous vapours-that it is a sort of Avernus, destroying birds and insects which pass in its neighbourhood; but I cannot endorse this view. I myself observed birds and insects flying over it with ease and impunity, nor was any noxious smell perceptible. Any ill effects could be produced only by the direct action of the steam, with which the sulphur could have little or nothing to do; and if any corroboration of this were required, it need only be mentioned that the patch occupied by the sulphursprings is immediately surrounded by the brightest verdure, and a stream of clear water runs along its edge and alone separates it from paddy-fields in the most green and healthy condition.

At the present time no attempt is made to obtain sulphur from this prolific source. Although it can be obtained at the rate of 45 cents per picul of 133 lbs. (about 2s. per cwt.), the Chinese government stupidly and obstinately forbid its being worked. Still sulphur has been largely obtained from these springs on the sly, or by means of a bribe, and it yet remains for European enterprise to open up so important and probably almost inexhaustible a source of this valuable material.

11. On the GEOLOGY of BENGHAZI, BARBARY; and an AccoUNT of the SUBSIDENCES in its VICINITY. By G. B. STACEY, Esq.

[Communicated by the President.]

THE town of Benghazi is built on a sandy foundation with a superstratum of clay. It is protected from the sea by a reef of sandstone rocks, now only 2 or 3 feet above the level of the water.

Inside the reef, the water reaches nearly to the clay cliffs, on which, during the winter gales, it has a very destructive effect.

Fifty years since, according to the testimony of natives, horse-races were held inside the reef, where now the water is in some places 5 feet deep; and, according to a European inhabitant, only a small strip of water existed there twenty-five years ago.

On the reef, remains of buildings are to be seen under water; and at Juliana Point the sea has made a breach, forming an island of the point, between which and the mainland the water is very shallow.

Hamilton, in his Travels in North Africa,' mentions that the land has sunk, and supposes a sudden catastrophe; but, from the above and other evidence, I imagine that the land is sinking regularly, and comparatively quickly.

Small hills of sandstone exist to the north-east and south-east of the town, and are quarried for the stones of which the town is built.

The fundamental rock of the country is a Tertiary limestone, in which several interesting subsidences have occurred, some of which (the "Gardens of the Hesperides" of Beechey) are cultivated; others, more extensive, are filled with brackish water, and contain a large eel and another fish of small size.

The following is a brief description of a few of the lakes which I have examined.

"Howa Bugedah" is about one-third of a mile in circumference, W.S.W. slope to water; rocks perpendicular E.S.E. to S.W. Greatest height of sides about 30 feet. Depth of water round the edges 11 feet N., 10 feet S., 15 feet E., from 13 to 14 feet W.; small cave on the south-east side.

"Howa Mumlood," 150 yards to the eastward of the above, is about half a mile in circumference; N.E. slope to water; sides perpendicular N.E. to S.E., about 30 feet high; depth of water 6 feet N., 9 feet W. On the south-east the rocks are much rent and slipped towards the water, leaving small chasms.

"Howa Mingernat," about 200 yards further east, is about one mile in circumference. The sides have more of a slope inwards, and are much more weathered than the others. On the south-east side is a small bay, the water of which is milk-coloured, being probably shallow and charged with carbonate of lime. The rocks slope downwards on the N.N.E. side, where it joins by a shallow channel another lake, bearing the same name. Sides perpendicular, cracked, and fallen in on the E. and N.E. About a quarter of a mile in circumference.

"Howa Buhowsh," about 300 yards north-west of the latter, has an island in the middle, separated from the north-west side by only shallow water. On the south-east side the rocks are much split and detached. Small caves in the fissures.

In "Howa Mumlood" on the N.N.W. side, a thin layer of coarse sandstone contains angular pieces of a black foreign rock, small pieces of bone, and a flint with a polished under surface, appearing as if it had been ground to a point. These materials were apparently washed in through a fissure, as the layer is not continuous. Besides the above, many smaller subsidences have occurred; in fact, the face of the country may be said to be dotted with them. The causes of these subsidences may probably be explained by examining a series of caverns containing fresh water and called "the Lethe," of which the accompanying section may give a sufficiently correct idea.

Section of "the Lethe" Caverns.

The slope in this case leads by a low entrance into a cavern, which leads by a narrow passage into another, where a huge block projects from the water. This leads again into another cave by a low entrance, and this may lead to others; but the rocks were so near the water that I was unable to proceed further with the boat. Stalactites hang from the roof.

The caves are probably reservoirs of the rain-water which runs

down the declivity in winter; this being out of the influence of the sun, but little evaporation would take place.

In the above case, we must suppose a cavern to have existed at x; the roof having fallen in has left a series of caverns exposed.

If we imagine this to have occurred on a larger scale, we have, I think, the true cause of the larger subsidences, all of which have, at one part or another, a slope to the water similar to the above.

The whole country must be cavernous; and the brackishness of the water of the lakes may be due to a connexion with the sea.

"Howa Bullowsh" may have been formed by two subsidences. Of the fossils collected, I have only been able to identify Echinodermata, 3 sp., Ostrea, 2 sp., Coral, 2 sp., a Pecten, a worm in the form of a Helix, and, on the surface, Cardium edule.

12. Report on the EXISTENCE of a large COAL-FIELD in the PROVINCE of ST. CATHERINE'S, BRAZIL. By EDWARD THORNTON, Esq. [Communicated by the Rt. Hon. the Secretary of State for Foreign Affairs.] THE Tubarao basin is situated in the southern extremity of the province of Sta. Caterina, lat. 284° S., long. 54° to 6° W. of Rio de Janeiro, and 48° 14' to 48° 44′ W. of Greenwich, distant about forty-five miles north-west of the seaport of Laguna, and intersected by the river Tubarao and its tributaries, which stream is navigated by small vessels for about twenty-five miles.

The existence of coal in this district has for some years been an established fact; and the Belgian traveller, Van de Lede, in 1842, visited and reported upon the small seams which were exposed to view on the route from Laguna to Lages; but from 1861 to 1863 a practical exploration was carried out by the Viscount Barbacena (who engaged Mr. James Johnson, an experienced Lancashire coal-viewer, and the engineers Messrs. Borell and Klap), which resulted in his purchase of a tract of land containing the best seams, and his acquisition of a concession of mineral rights in the valley of the Tubaraõ from the Imperial Government, dependent upon the formation of a railway and the opening of the mines.

The exploration, by driving several levels and sinking pits over an area of about twelve miles, proved the existence of a series of Coalbeds at nine different levels, underlying a sandstone formation, in almost horizontal strata of different qualities, and of thickness varying from 1 to 10 feet, all more elevated than the waters of the adjacent

streams.

The longest adit was driven 78 feet through coal, which proved similar to that exposed in two other outcrops three miles distant from each other, showing, under a solid roof of grey sandstone,—

making 10 feet 3 inches of Coal of good quality, the main seam being extremely hard and, like Cannel Coal, igniting readily; it is also of great heat-producing capacity, but leaves more ash than the best English coals.

An analysis of samples from two seams, made by Professor Thomas Richardson in London, exhibited the following results::--

These figures give the number of pounds of water which 1 lb. of coal can evaporate from the boiling-point. The best English steamcoals evaporate as much as 12.50 lbs.

To the immediate fruition of so valuable a property the present obstacle is the want of means of transport, which by survey has been ascertained to be obtainable by a tramway of thirty-seven miles from the centre of the Coal-field to a navigable part of the river Tubaraõ, where ships of 600 tons burden might take cargoes.

13. On the SOURCES of the MATERIALS composing the WHITE CLAYS of the LOWER TERTIARIES. BY GEORGE MAW, Esq., F.G.S., F.L.S., &c. IN examining some light-coloured deposits that occur between the Boulder-clay drift and the Carboniferous Limestone of North Wales, an account of which has recently appeared in the Geological Magazine*, I was led to the conclusion that some of the beds of very white and pure clays occurring in "pockets" in the limestone could not have been derived from the mere mechanical degradation of any previously existing materials; and an analysis showed that they consist of silica and alumina in nearly similar proportions to the silica and alumina in the limestone, and, therefore, that they were probably left behind after its calcareous matter had been removed by watery dissolution.

The Tertiary formations of Hampshire, Dorsetshire, the Isle of Wight and Devonshire, contain vast deposits of similar white clays; and I beg to lay before the Society a few facts bearing on the probability of their having had an analogous origin by the dissolution of the calcareous portion of the chalk.

* Vol. iv. pp. 241 and 299.