preceded by a fenfible increase in its internal roarings. M. D'Orville was not intimidated by them, he knew that Etna feldom cafts forth flames and ftones; befides, every thing generally falls back into its vaft mouth. In fhort, the motion did not laft; after a moment's dilitation, as if to give it vent, the volcano refumed its tranquillity. But this phænomenon might return, and the wind, which drove the vapours to the north, might, by changing, bring them to the fouth, in which cafe our curious obfervers would have run fome risk of being fuffocated, as Pliny the elder was by Vefuvius. They therefore went towards their attendants, and immediately got to the top of that enormous heap of lava and ftones, of afhes and fulphur, which, having been accumulating for fo many ages, have raised mount Etna above all Sicily.

Though few are capable of defcribing fo well as M. D'Orville, the immenfe and wonderful scene which prefented itself to his view the moment that the fun had rifen above the horizon, yet it is eafy to form from his defcription fomne idea of this grand appearance. Our author could fearce tear himself from it. No delay, fays he, would have feemed long to me, contemplating, as it were, at one view, the true fituation of fo many countries, cities, towns, hills, plains, iflands, coafts, and feas; if my companions, fatigued with the journey, had not admonished me, tired as I alfo was, to ⚫ defcend the mountain.' Once or twice he ftil delightfully looked about him with eyes full of admi

ration, in order to imprint the profpect in his mind, and never to forget its inexpreffible beauties. 'Once and again, therefore, fays he, 1 enjoyed the unparalleled plea'fure of that view, never more to 'be repeated, and fatisfied my eyes and my mind for the remainder of my life.' At laft he left it, and having foon defcended to the place where was the piece of marble, formerly mentioned, he there remounted, congratulating himself on the good fuccefs with which his curiofity had been repaid.

Observations on the singular phænomena of disappearing and reappearing rivers: with a description of several such rivers in Normandy, and other parts of France. From a memoir by M. Guettard, in the last volume of the history of the Royal Academy of Sciences at Paris,

TH

THE farther we enquire into the works of nature, more have we reafon to admire them. It is remarkable alfo that our admiration arifes more frequently from thofe effects we have been accustomed to fee, than from our not being able to comprehend them. It is very furprifing, if we reflect on it, that a river in its courfe, which is often very extenfive, fhould not meet with fpongious foils to fwallow up its wa ters, or gulphs in which they are left: neverthelefs, as there has been hitherto known but a small number of rivers whose waters thus difappear, this phænomenon has been accounted very extraor

dinary,

dinary, both by the ancients and moderns. Pliny fpeaks of it with an energy familiar to him; and Seneca mentions it in his Quæf tiones Naturales: he even diftinguifhes thefe rivers into two forts, those that are loft by degrees, and thofe which are swallowed up all at once, or ingulphed: which would make one believe that the ancients had collected fome observations concerning them.

But leaving apart what may be wonderful in these rivers, it may be afked, how they are loft? From what particular qualities of the foil over which they flow, and from what fituation of the places through which they pafs, does this phænomenon arife? Upon this head we find but little light in authors. We might, perhaps, be informed a great deal more, if the obfervations of the ancients had reached us.

Mr. Guettard has undertaken to remove parts of this obfcurity by defcribing what he has obferved in feveral rivers of Normandy, which are loft and afterwards appear again; these are five in number, viz. the Rille, the Ithon, the Aure, the river of Sap-Andre, and the Drôme.

The three first disappear gradually, and then come in fight again; the fourth lofes itself entirely by degrees; but afterwards re-appears; the fifth lofes fome of its water in its courfe, and ends by precipitating itself into a cavity, from whence it is never seen to rife again.

What feems to occafion the lofs of the Rille, the Ithon, and the Aure, is the nature of the foil through which they pafs. M. Guettard has obferved that it is

in general porous, and compofed of a thick fand, the grains of which are not well compacted together; it finks fuddenly down by its own weight in fome places, and there forms great holes; and when the water overflows the meadows, it frequently makes many cavities in feveral parts of them. If we therefore fuppofe inequalities in the channels of these rivers, and that there are certain places in which the water ftagnates longer than in others, it must there dilute the ground, if we may use that expreffion; and having carried away the parts which united the grains of fand together, thofe grains will become afterwards no other than a kind of fieve, through which the waters will filtrate themfelves, provided nevertheless that they find paffage under ground through which they may run. This conjecture appears to be fo well founded, that each of thefe three rivers lofes itself nearly in the fame manner, that is, through cavities, which the people of the country call betoirs, and which fwallow up more or lefs according to their largenefs. M. Guettard, who has carefully examined them, remarks that thefe betoirs are holes in the form of a tunnel, whose diameter and aperture is at leaft two feet, and fometimes exceeds eleven ; and whofe depth varies in like manner from one and two feet to five, fix, and even twenty. The water generally gets into these cavities, when the river is not very high, making a guggling noise, and turning round in an eddy. A proof that waters are there filtered and abforbed among the grains of this fharp diluted fand, is, that frequently in a betoir two or three H 2

fest

feet deep, and through which a great deal of water is loft, one cannot thrust a stick farther than the furface of its bottom. Wherefore as these betoirs fo frequently occur in the bed and banks of the Rille, the Ithon, and the Aure, it is not surprising that these rivers fhould be thus loft. The Rille during the fummer feafon lofes almost all its water in the fpace of two fhort leagues; the Ithon does very near the fame; but M. Guettard obferves fomething curious concerning this river, to wit, that formerly it was not loft, but kept its courfe without any interruption, as appears by the hiftory of the country very likely, the mud which had been collected together in feveral parts of its channel, might have occafioned the waters remaining in others, and thereby have caufed many betoirs. This is the more likely, as the mud having been collected together in the bed of the river Aure, it appears that, in confequence thereof, the cavities were greatly increafed, which makes it lofe itself much fooner than formerly; however it has been refolved to cleanfe its channel to remedy this inconveniencé. Befides, poffibly an earthquake happening in the country might have caufed feveral fub

terranean canals through which the water of the Ithon (which before very likely could not pafs through the foil beneath its bed) has forced its way. In effect it appears that a foil's being porous is not fufficient to caufe the lofs of a river; for, if it were then to do fo, it would occafion many fens round about, nor would it renew its courfe after having difappeared

a certain time: it must befides, as we have before said, find ways under ground, through which it may take its courfe. M. Guettard feems alfo much inclined to believe that there are, in these parts, fubterraneous cavities through which the waters may flow; and in confequence of this he reports a number of facts, all tending to prove the truth of it, or at least to prove that there must be hollow quarries ferving for ftrainers to thefe waters. Upon which occafion he goes into a difcuffion of this question: Are there any fubterraneous rivers, and is the prepoffeffion of fome perfons in favour of this particular well-founded? He makes appear by feveral inftances which he quotes, and by many reasons which he alledges, that there are at least very great prefumptions in favour of this opinion. We are too apt not to look beyond the exterior of things: we feel refiftance upon the furface of the earth; when we go deep we often find it compact. It is therefore hard for us to imagine that it can contain fubterraneous cavities, fufficient to form channels for hidden rivers, or for any confiderable body of water; in a word, that it can contain vaft caverns; and yet every thing feems to indicate the contrary. A fact that is obferved in the betoirs of the ri vers concerning which we have fpoke, and particularly of the Rille, proves in fome measure that there are confiderable lakes of water in the mountains which limit its courfe; this fact is, that in winter the greateft part of their betoirs become fprings, which fupply a-new the river's channel with as much water as they had abforbed from it during the fummer. Now,

from

from whence can that water come, unless from the refervoirs or lakes that are inclosed in the mountains, which being lower than the river in fummer, abforb its water, and being higher in winter, by occafion of the rain they receive, fend it back again in their turn?

M. Guettard ftrengthens this conjecture by feveral inftances that render it very probable; he remarks, at the fame time, that this alternate effect of the betoirs fwallowing up the water and reftoring it again, caufes perhaps an invincible obftacle to the reftraining of the water within the channel of the river. It has indeed been feveral times attempted to ftop thofe cavities, but the water returns with fuch violence in winter, that it generally carries away the materials with which they were stopped.

The river of Sap-André is loft in part, as we have before said, in the fame manner as the Ithon and the Rille; but there is fomething more remarkable in it than in thofe rivers; to wit, that at the extremity of its courfe, where there is no perceptible cavity, it is, as it. were, ingulphed, but without any fall the water paffes between the pebbles, and it is impoffible to force a ftick into that place any further than into the betoirs of which we have spoke. What makes this river take that fubterraneous direction, is an impediment which its ftream meets with in that place: it is there ftopped by a rifing ground fix or feven feet high, whofe bottom it has very likely undermined, to gain a free paf fage, not having been able to make its way over it. At fome distance from thence it appears

again; but in winter, as there is a greater quantity of water, it paffes over that eminence and keeps an uninterrupted courfe.

Laftly, the Drôme, after having loft fome of its water in its courfe, vanishes entirely near the pit of Soucy; in that place it meets with a fort of fubterraneous cavity near twenty-five feet wide, and more than fifteen deep, where the river is in a manner ftopped, and into which it enters, though without any perceptible motion, and never appears again.

We fee by thefe obfervations of M. Guettard, that rivers which lofe themselves are not fo few as it is generally imagined, fince there. are five of them in this part of Normandy, which is but of fmall extent. One might fancy that this is owing to the nature of the ground; yet M. Guettard obferves, that in a part of Lorrain, which likewife is not very extenfive, five other rivers are known to lose themselves in the fame manner and without doubt we shall find by new observations that they are much more common; for as we have remarked, it perhaps is not more furprifing that a river lofes itself, than it is extraordinary that it does not fo.

M. Guettard finishes this memoir with fome obfervations upon the lerre. This river is loft in the fame manner as the Rille; and though it is very near Paris, this fingularity is unknown to almost every body; were it not for the account of M. l'Abbé le Bœuf, M. Guettard would have been alfo ignorant of it. And as he thinks the chief objects of a naturalift's obfervation ought to be the public good, he examines the means H3

which

which might be employed to reftrain the water of the lerre. The fame object has made him add a defcription of the manner how the Rône is loft, or rather how its courfe is difturbed; for it is now very certain that it does not lose itself, but that its channel is extremely confined in the place where it was pretended that it loft itself, by two mountains, between whofe feet it runs. M. Guettard makes it appear that it might not be impoffible to widen that place, and give a fufficient channel to the river; which would render it navigable, and be of vaft utility to all the country.

We may add to the above account, that we have in Surrey the river Mole, which rifes in Darking hundred, and, after a confiderable courfe, paffes by Witchill, near Darking; a little beyond which this river hides itself, or is fwallowed up in a cavern at the foot of the hill, from whence Cambden fays it is called the Swallow; he alfo takes notice of its running under ground for about two miles, and rifing again, and fpreading itfelf into a wide ftream. It is alfo frequently reported that there are feveral of thefe dipping rivers in Wales, and others in the fouthern counties of England.

An account of the Plague at Aleppo. In a letter to the Rev. Charles Lyttelton, LL. D. Dean of Exeter, now Lord Bishop of Carlisle, and F. R. S. from the Reverend Mr. Thomas Dawes, Chaplain to the Factory at Aleppo. From the Philasophical Trans. for 1763.

"THIS unhappy country for fix years paft has been in a

very terrible fituation, afflicted` during the greatest part of that time with many of the Almighty's fevereft fcourges. Its troubles were ufhered in by a very fharp winter, in 1756-7, which deftroyed almost all the fruits of the earth. The cold was fo very intenfe, that the mercury of Fahrenheit's thermometer, expofed a few minutes to the open air, funk entirely into the ball of the tube. Millions of olivetrees that had withstood the feverity of fifty winters were blafted in this, and thousands of fouls perifhed merely through cold. The failure of a crop the fucceeding harveft, occafioned an univerfal fcarcity, which in this country of indolence and oppreffion (where provifion is only made from hand to mouth, and where, literally speaking, no man is fure of reaping what he has fown) foon introduced a famine, with all its attendant miferies. The fhocking accounts related to me on this subject would appear fabulous were they not confirmed by numberless eyewitneffes, both Europeans and natives. In many places the inhabitants were driven to fuch extremities, that women were known to eat their own children as foon as they expired in their arms for want of nourishment. Numbers of perfons from the mountains and vil lages adjacent came daily to Aleppo to offer their wives and children to fale for a few dollars to procure a temporary fubfiftence for themfelves and hourly might be feen in our ftreets dogs and human creatures fcratching together on the fame dunghill and quarrelling for a bone or piece of carrion to allay their hunger, A peftilence followed clofe to the heels of the

:

famine,