I temperature, termed by fome philofophers the internal heat of the earth, is always above the freezing point, as is evident from the heat of the fprings which ilue from the bowels of the earth. In winter therefore, or in thofe high regions of the globe where the cold is ufually below the freezing point, when any fpot of gr und is covered with only a thin coat of fnow, it may be fo far cooled, to a certain depth, by the influence of the external air, as not to be capable of diffolving any part of the fuperincu bent now. But when the mafs of fnow is of fuch a thickness as to protect the furface of the ground from the effects of the atmospherical cold, the mean temperature, which is always above the freezing point, will be fufficient to melt the conti uous furface of fnow, and to occafion a confiant thaw, which applies thofe currents of water that flow, at all feafons, from the Upper and Lower Glaciers. "In regard to the argument de rived from experience, it is fuffi cient to obferve, that while 1 admit the facts which prove the progre's of the ice, it by no means feems to follow that its fum is perpetually in creating. For the advocates who fupport this opinion, while they fcrupulously enumerate the places which have been invaded by the ice, do not take any notice of thofe parts, no lefs numerous, from which the ice has retired. During my fecond expedition into the Alps, Lalfo made this pont of controverfy a particular object of my releaiches; and on enquiring from the coafieurs, aud other perfous who frequent the mountains, the greatest part were of opinion that the collection of ice and fnow even in the elevated regions, was by no means in a continual state of aug, mentation; but that while it gaired in fome places, it dia inifhed in others; and that upon an average, the aggregate mafs was nearly the fame," ACCOUNT of a fingular SPECIES of VOLCANO. A [From M. Da Nox's Travels in SICILY and MALTA.] N Agrigentine, named Gubernatis, with whom I had become a quainted, and to whom I was indebted for great part of my informen refpeing that city, conducted me one day to one of the most interefting curioiies of the country, and which has hitherto been peglected by all modern ravellers; it is a volcano of a peculiar fpecies, not refembling any other, either in its eruptions, the matter it cinits, or the form it affumes. "This phænomenon is fituated between Aragona and Girgenti, fix miles from the latter and four from the former. It was known to Soli, nus and Fazello, who have both mentioara it. In the time of the later, the place was called Mayharuca; its prefent name is Macalubba. For foveral ages paft it mani felled itfelt fo outcurely, and with fo Lttle noife, that it was forgotten, and no longer known to any but the poffeffor of the eftate is lies in. But laft year, on the 29th of Septem ber, 1777, at funfet, a column of thick fmoke iffed from the centre, which continued rifing till fix in the morning of the next day, wher, by a terrible explosion, it opened itself a mouth a mouth, from whence it fhot forth into the air, with a tremendous noife, a column of fine potters earth, which rofe to the height of above fixty eet, fome fay twice as high; and fpreading into the form of a muthroom divided an I cover d part of the orifi e from which it had proceeded, while the remainder returning back to its centre, occafioned by its fall, a deep and rumbling rear, which was foon followed by a frefh exploton. Thefe throes continned at intervals of every fix minut s'; and an hour and a half after, it recommenced with more violence than ever, fo that in the fix hours it lafted, there were four diftinct eru, i ns, which covered with clay a pace of two hundred and fifty feet in diameter. The foil was not raifed by it above three feet, the matter being to attenuated, as to fpread in falling, and flowing like a lava, on the neighbouring emi nences, filling up their cavities. The mouth having been filled by this matter, there remained no more appearance than before of a volcano. Thefe eruptions happened eleven months before I visited the place. The propri tor of the ground, who had been an eye witnefs of them, was fo god as to accompany us, and to communicate to me all the particulars I have related. We exmined the place together, but could difcover nothing but a cavity fearce ly perceptible, covered with a cruit, baked and cracked by the heat of the fun. Upwards of lixty apertures, from four to fix inches in diameter. maniffted the conftant exertion of a fubterraneous power, by a perpetual ebullition of falt water, mixed with an almost impalpable clay, iffaing every instant from thefe apertures, the matter fubfiding and rifing, like coffee boiling in a kettle, Round each mouth little craters were formed in hape of cones, which the fluidity of the matter prevented from rifing to above fix or feven inches, and from thefe craters flowed little fluid lavas, which infinuated themfelves into, and were loft in the chinks; the whole abfolutely forining the reprefentation, in miniature, of a volcano, with ali its wonderful phænomena. "I was fo anxious to examine it, that approaching too near and hástily, my fe broke the cruft, and I was ready to fiok into the clay. I proceeded with more caution theretore to another aperture, and laid myfelf on the ground, in order to prefent a greater furface, and have a Lear view. I applied my car to the ofice, and heard no internal noife, but a ticking exactly like that produced by fmali fparks drawn from the conductor of n clectrical machine. I found that this noife was occafioned by the explofion of the ar bubbles which were continually dilating, and that the noife of the dilatation was ftronger than in ordinary water, in proportion to the weight and density of the matter whence they procceded. Thefe buobles were fometimes powerful enough to make an explofion four inches above the mouth. The air that evaporated from it had the fmell of a brick kiln newly opened. I applied my tongue to the fluid matter, and found nothing but the tate of tea-falt, only a little acrid. "I clofed one of the apertures perfect y tight with my hand, and felt the pretture of the air repelling it; the mat er now efcape more abundantly from the adjoining mouths, and the air fwelled under my ha d, o that in hitting it, it was followed by a toife like that of the air p mp after a flight froke of the pitton; which evidently proves a general communication of all the apertures. Another proot is, that not to be attenuated by time. Since, notwithstanding the antiquity of the other eruptions, whofe date is unknown, there is little or no vegetation in all the fpace in which these apertures are found. This rock flone, and talc, and thefe minerals, which do not partake of the nature of the clay they are found in, prove that under the bed of this fluid earth, there is a rock, below which lies the principle of this phænomenon. The air bubbles, the odour they exhale, the tepidity of the water, and above all, the fposting and noify eruption of latt year. leave no room to doubt of the caufe being volcanic. that on our advancing to the centre, the weight of four perions preffing on the cruft, made the matter iffue more plentifully at once from every crater. I ftill proceeded to examine fome new ones; in fome of which I found marks of a bituminous mire, and in all of them a marine falt elaborated by the fun, and fpread over the furface of the earth. I introduced my hand into one of the holes, and found the matter tepid like the water of a warm bath. I tried to found the depth of it with my cane of fix feet long, which entered without the least refiftance, and gave no figns of a bottom. I then tried a fecond time the thickness of the cruft, and finding it but fix inches at the apertures, began to perceive the danger of making obfervations on this phænomenon, lefs dreaded, but more dangerous that any of the kind; for remaining fome time in the fame place, I diftinctly perceived that the repeated preffure of the foot moistened a frefl, and diluted this cruft, which if it happened to give way must inevitable precipitate us into a hot mud, where we fhould meet with unavoidable and dreadful death. We finished our examination of this place therefore with the greatest precaution. I remarked, that this volcano not only threw forth moistened earth, but stone, and a fpecies of baked earth of little confiftence, which the air deftroys and separates into flakes. I obferved likewife different forts of talc, fome in leaf like crystal, and found iron ore and marcafite, with the efflorefcence of copper; and on examining the lands adjoining to the voleno, met with the fame productions. In fome places too there was a crust rendered hard and folid by rime, and fmall mouths producing the fame effects, and this at a great dishince from thofe of the eruption of 1777. I picked up a falt there, "It I might be allowed to hazard any conjecture of my own, concerning the couf of a phænomenon with which we are fo little acquainted, I fhould fay that he fubterranean fire that reigns throughout this part of the ill-nd, from Siacda hither, meets int's place with fome falt fprings, which tu' rilizing a light earth, loves here, more readily than elfew here a paffage for the air, produced by this fire; that this paffage of the air, continually fitting, mingling, and attenuating more and more this earth, by its continual best, it becomes at length fo elaborated and light, as to give way to the power that raifes it, and that immediately after the volcanic evaporation, this humid matter, falling back on itfelf, refumes in its turn the power it had loft on the volcano; and that here, in fort, as at the ftoves of Sciacca, and in the country round Palma, where a great deal of fulphur is fabricated, we can difcover only the principles of a volcano, the materials of which apparently are neither fufficiently abundant, or complete, nor renewed often enough, to produce the great effects of Vesuvius and Etna.? MODE MODE of CULTIVATING and GATHERING MANNA at CARINI.. “A [From the fame Work.] Great quantity of excellent manna is collected at Carini, which oozes from a fort of afhtree, the leaf of which in fhape bears fome refemblance to that of the acacia, and the bark in its texture to that of the ebon-tree. I had before found manna trees at Termini and Palermo; but they appeared to me fo young, that I took them for nursery plants. I found here, however, that youth is the period of abundance with this tree, in which, as foon as it is feven or eight years old, and has grown to the height of eight feet, they begin to make horizontal incitions in the the bark, from whence flows the manna. This operation is repeated every two days, from the fifteenth of July, until the rains or fogs of autumn fufpend the circulation, or adulterate the quality of this glutinous gum.Thefe incifions are made one above the other, from the furface of the earth to the top of the tree, and the operation is daily repeated as long as the featon permits. The liquor first appears like a white froth extremely light, pleafing to the palate, and of a very agreeable flavour. The heat of the fun coagulates this frothy juice, and gives it the form of it lactites. This is what they call lachrymatory or canc manna; the dearest and finest fort. It remains almoft white, and the glutinous and more highly coloured liquor that now difils from it, is received on leaves of the Indian fig, placed for that purpofe at the foot of the tree. This too becomes at length congealed by the fun, and being then taken up in lumps, forms what is called fat manna, which is heavier, more purgative, and of much lefs value. It is this part of it alone, which, when fresh, poffeffes that faint and difagreable tatte fo difgufting in manna; for that in cane, eaten off the tree, is of an agreeable flavour, and an excellent ftomachic. The latter is detached from the bark by bending the tree and shaking it. When the feafon is rainy, the quantity produced is confiderably lefs, and they are obliged to gather it every day, which occafions it to be lefs fine and clear; that which has been wet is worth nothing, and corrupts. The method of multiplying this tree is to fow it, and tranfplant when at the height of three or four feet. When the ftem is entirely covered with incifions, they cut it down close to the ground, and it pufles forth tufts of young wood, of which they preferve one or two fhoots on each fucker, on which they repeat the former procefs. The wood is hard, heavy, and bitter, and the decoction of it aperitive, and of great efficacy in the dropfy. Every climate is not adapted to the culture of this tree. It is productive only in hot countries, and does not thrive, unlefs where it is exposed to the north winds. This part of the ifland only produces manna, which, though lefe celebrated than that of Calabria, is dearer, and preferred to it. fuperiority may arife from its being a native production in Sicily, and confequently thriving better there ; and the celebrity of the Calabrian manna, from its having been there more anciently known and cultivat ed. I am perfuaded that this tree would thrive in France, and produce manna in Provence." The RULES RULES for predicting CHANGES of the WEATHER by the BAROMETER. [From the LITERARY MAGAZINE for October 1790.] THE HE rifing of the mercury prefages, in general, fair weather, and its falling, foul weather, as rain, fnow, high winds and ftorms. "2d. In very hot weather efpecially if the wind is fouth, the falling of the mercury foretels thunder. 66 3. In winter the rifing prefages froft, and in frofty weather, if it fails three or four divifions, there will tollow a thaw; but if it rifes in a costnued frott, fhow may be expected. "4th. When foul weather happens foon after the falling of the mercury, expect but little of it; and the fame inter, if fair weather fucceeds flortly after its rife. 5th. When the mercury continues to rife for two or three days before the foul weather is over, ex pect a continuance of fair weather to follow. 6th. In fair weather, when the mercury falls much and low, and continues fo for two or three day's before the rain comes, then expect much wer, and probably high winds. 7th. The mercury generally rifes very faft after great storms of wind, when before it was very low. Dr. Hailey mentions that he once abserved it to rife an inch and a half in fix hours, after a long continued ftorm of fouth-west wind. 8th. The unfettled motion of the mercury indicates uncertain or changeable weather. "The words on the plate are not ftrialy to be adhered to, though they will in general agree, for the height of the mercury does not fo much indicate the weather as its motion up and down; to know therefore whether the mercury is actually rifing or falling, observe, "rt. If the furface of the mercury is convex, (tanding high in the middle) it is then rising. "2d. If the furtace is concave, (ftanding low in the middle) it is then falling. "3d. If the furface is plain, or a little convex, it may be confidered as stationary. "4th. A finall flake of the tube will fometimes bring the mercury to its approaching height. "The foregoing rules are chiefly to be depended upon; but the following are not unworthy of regard. t. The greatest heights of the mercury are on easterly and north-easterly winds, and its lowest ftation on foutherly or wefterly winds. 2d. A continuance of fair weather, the wind being in the north, and the mercury high or riding, is never fucceeded by rain till the wind changes foutherly. "3d. A continuance of rain from the fouth is fearce ever fucceeded by fettled fair weather, before the wind changes either to the weft or fome point of the north. 4th. If the mercury falls when the wind is full fouth, it fcarcely ever fails, to be a fign of rain. "5th. If it is going to be cold, frofty, or foggy, it rifes pretty high; but if going to be winds or tempeftuous, it will then fink very low, and as foon as the first form is over rife again apace. "The barometer never fails to flew the true caufe of the altera |