gave no other produce than what might be expected from a resinous body; the caput mortuum, when burned and elixated, yielded a fixed alkali; to this may be attributed the moisture which the pitch, that was in contact with the spine, and those other parts which were most burned, contracted on being broken and exposed to the air; for this pitch had an alkaline taste, and had been more than melted, having been burned to a caput mortuum. A great variety of experiments were made on this pitchy matter: the result of them all tended to prove, that it had not the least resemblance to asphaltus, but was certainly a vegetable resinous substance.

Observations on the Proportion which the Decrease of Heat bears to the Height of Situation. BY THOMAS HEBERDEN, M.D. F.R.S.—[1765.]

THE remarkable transition from heat to cold in all seasons, in proportion as we ascend Teneriffe, induced Dr. H. to make the following observations, with intention to discover if there subsists any regularity between the difference of heat and the elevation of situation. Some persons were supplied by him with the proper instruments, and their watch adjusted by his regulator: they were instructed to remark the hour and minute each observation was made, and, on their return, their observations were compared with the height of the thermometer and barometer in his study at the time of the observation, of which he had kept an exact account during the journey. From which observations he formed the following table, supposing the descent of the barometer of an inch for every 90 feet:

Though the different degrees of heat in different places must depend greatly on the accident of situation, with regard to mountains, vallies, and to the different soils, &c. yet there is so much regularity in the above observations, that perhaps

we shall not err much in computing, where the soil and surface are tolerably uniform, "the decrease of heat, by Fahrenheit's thermometer, in the proportion of one degree for near 190 feet of elevation on this island."

On the Nature and Formation of Sponges. By JOHN ELLIS, Esq. F.R. S.-[1765.]

AMONG those animals commonly called zoophytes, we may plainly discover an evident approximation, from the rudest irregularly formed sponge, which is the lowest being yet observed to have the appearance of animal life, to the most beautiful and elegant red coral. The nature and formation of sponges having never yet been thoroughly investigated, every attempt to explain this dark part of nature must give satisfaction to the curious.

In the year 1762, when at the sea-side at Brighthelmstone, he dissected carefully the crumb of bread-sponge, in hopes of discovering the small animal that was supposed to fabricate them; and was surprised to find a great number of small worms in them, particularly a very small kind of nereis, or sea-scolopendra; but these worms appeared evidently, instead of being the fabricators of it, to have pierced their way into its soft substance, and made it only their place of retreat and security. After this, he proceeded along the sea-coast to Little Hampton, near Arundel, on the coast of Sussex, where he took up out of the sea several specimens of the same sort of sponge full of an orange-coloured gelatinous matter; and, while they were just fresh from the sea, examined them, after they had rested for some time, in glasses of sea-water; and to his great surprise, instead of seeing any of the polype-like suckers, or any minute animal figure come out of the papillæ, or small holes with which they are surrounded, he only observed these holes to contract and dilate themselves. And as a further confirmation of this motion, being at Hastings, in Sussex, in August, 1764, he collected from the rocks, at ebbtide, just under water, a variety of the same kind of sponge, but of a pale yellow colour, and in the form of several cocks' combs united together, the tops of which were full of tubular cavities, or papillæ; when he examined these in glasses of sea-water, he could plainly observe these little tubes to receive and pass the water to and fro; so that the sponge is an animal sui generis, whose mouths are so many holes or ends of branched tubes opening on its surface; with these it receives its nourishment, and by these it discharges, like the polypes,

its excrements.

The connected tubes of both arise from the part to which they adhere to the rocks, &c. Hence both kinds branch out and swell into irregular lobes; with this difference, that the surface of the sponge is covered with holes guarded with minute points like little spines; the surface of the alcyonium with starry openings of eight rays, whence the polype-like suckers are protruded, to find out proper nourishment: and these starry openings in one, and the holes in the other, so far correspond, that in both kinds they are found of different sizes; but this is in proportion to the age of the branching tubes that come to the surface.

In the sections of the alcyonium may plainly be distinguished the reticulated elastic fibres, that enclose the transparent stiff gelatinous part, as in the sponges; but as this gluey substance is of a firmer texture than what is found in sponges, it requires more pains to separate it from the elastic fibres; however, with a little trouble it may be done sufficiently to evince what he has endeavoured to prove, viz. the great proximity there is between the animal life of sponges and alcyoniums, and, consequently, that both are animals.

Before concluding, he endeavours to remove some doubts, which seem to have distressed the generality of curious persons to account for; the one is, What occasions those very large holes that appear here and there irregularly on the surface of most sponges? the other is, How came those extraneous bodies, such as small shells, stones, and even parts of fucuses, in the middle of these animal bodies? In answer to the first, on cutting open and examining these bodies while recent in sea-water, as before shown, we frequently find a variety of different worms, who bore their way into them, and make their nests and retreats there, or perhaps to live on the gelatinous part of the sponge. But he says, these are not the fabricators, but the inhabitants; and allows the alcyonium to be of animal origin, in which he says he has discovered evident marks of sensation. As to the second doubt, it may be observed by the curious enquirer into nature, that the same property of inclosing extraneous sub

stances is common to the whole class
of zoophytes, as they grow up, from
the
sponge to the red coral.

A is an irregular piece of the crumb of bread-sponge, found at Pagham, on the sea-coast of Sussex; a represents the papillæ, through which the sponge receives and dis

charges the water: this, when recent, is of a fine orange

colour.

B is the branched English sponge: along the edges, and on

the surface of the branches, are rows of small papillary holes, through which the animal receives its nourishment.

C represents the downy-branched English sponge found on the Sussex coast; this is covered over with a fine down so close, that it hides the many small holes that are on its surface.

Description of Mount Sinai. By E. W. MONTAGUE.

Ar Suez he found an opportunity of going to Tor by sea, which he gladly embraced, that by going nearer the place at which the Israelites are supposed to have entered the gulf, and having a view from the sea, as well of that as of the opposite shore, he might be a little better able to form a judgment about it. Here it is high water always when the moon is at her meridian height, and it ebbs six hours. At Suez, it flows six feet; the spring-tides are nine; and in the variable months, from the beginning of November to the end of April, sometimes 12. From the beginning of May to the beginning of October, a northerly wind generally rises, and goes down with the sun it is often very strong. This wind never fails in these months, unless there be some violent storm; the rest of the year the winds are variable; and when they blow hard at S. and S. S. E. these winds set up the sea through the narrow strait of Babel Mandel, and up this gulf through its mouth, between Gebel El Zait, on the west side of this sea, and the southermost point of the bay of Tor, on the east side of this western branch of this sea, where it is not above 12 or 14 miles over. Probably such a wind, hindering the water from going out, causes this extraordinary increase in the spring tides. The same thing happens with the same winds at Venice, both gulfs running nearly in the same direction.

The Egyptian, western, or Thebaic shore, from Badeah

southward to opposite Tor, on the eastern shore, is all mountainous, and steep; and at Elim, the northernmost point of the bay of Tor, ends the ridge of mountains, which begin on the eastern shore of this western branch at Karondel. The garden of the monks of Mount Sinai at Elim renders in dates, &c. 20,000 piastres per annum, or 2500l. Thence they crossed the plain, in about eight hours, and entered the mountains of Sinai. They are of granite of different colours. At the entrance of the narrow breach, through which they passed, he saw, on a large loose granite stone, an inscription in unknown characters, given, he thinks, by Dr. Pocock, Bishop of Ossory; however, as the Israelites had no writing, that we know of, when they passed here, he did not think it of consequence enough to stop for: they arrived at the convent of Mount Sinai, after the usual difficulties mentioned by other travellers, and were received as usual, and saw the usual places. The monks were far from owning that they had ever meddled with the print of the foot of Mahomet's camel. He examined it narrowly, and no chisel has absolutely ever touched it, for the coat of the granite is entire and unbroken in every part; and every body knows, that if the coat of less hard stones than granite be once destroyed, it never returns. It is a most curious lusus naturæ, and the Mahometans turn it to their account. Meribah is indeed surprisingly striking. He examined the lips of its mouths, and found that no chisel had ever worked there: the channel is plainly worn by only the course of water, and the bare inspection of it is sufficient to convince any one it is not the work of man. Among the innumerable cracks in rocks, which he had seen in this, as well as other parts of the world, he never met with any like this, except that at Jerusalem, and the two in the rock which Moses struck twice.

He enquired of the monks, as well as Arabs, about certain places, as well as about some ruins, supposed, by the Bishop of Ossory, to be Kadesh Barnea: the former could only tell him they had not received any fish from thence for many years; that it was two easy days' journey off, but the road was mountainous; so one may suppose the distance less than 40 miles. The Arabs agreed as to the road; but they said, it was once a large place, where their prince lived, whose daughter Moses married; that Moses was afterwards their prince, and the greatest of all prophets. These Arabs place Moses the first, Solomon the second, Mahomet the third, Christ the fourth, and then the prophets of the Bible. As to Dzahab, the monks only knew the distance to be four