a foreign particle, which ought to be confidered as the nucleus, or primary cause of its formation. The foofe pearls, may originally have been produced within the body, and on their incrcafe may have feparated and fallen into the cavity of the fhell. Thofe compact ones, fixed to the thells feem to be produced by fimilar extravafation, occafioned by the friction of fome roughnefs on the infide of the fhell. Thefe and the pearl-like nodes have a different afpect from the pearls, and are of a darker and bluer colour. In one of the former I found a pretty large, true oval pearl, of a very clear water; while the node itself was of a dark blueish colour. The yellow or gold coloured pearl, is the most efteemed by the natives; fome have a bright, red luftre; others are grey or blackish, without any fhining appearance, and of no value. Sometimes when the grey lamella of a pearl is taken off, under it is found a beautiful genuine one, but it of tener happens that after having feparated the first coat you find worthlefs impure pearl. I tried feveral of them, taking one lamella off after another, and found clear and impure by turns, and in an impure pearl I met with one of a clear water, though in the centre of all I found a foreign particle. The largest and most perfect pearl which I law during my ftay at Condatchey, was about the fize of a fmall piftol bullet, though I have been told fince my departure, many others of the fame fize have been found. The fpotted and irregular ones are fold cheap, and are chiefly

*The golden tong.

Weaver's fhuttle. tt Garter Aamper.

a

ufed by the native phyficians as an ingredient in their medicines.

Those that

We. may judge with greater or leffer probability by the appearance of the pearl-fhell, whether they contain pearls or not. have a thick calcareous cruft upon them, to which ferpula (lea-tubes) Tubuli marini irregulariter intorti, Crifa-gali Chamar lazuras, Lepas tintinabulum, Madreporee, Millipore, Cellipore, Gorgonte, Spongiæ, and other Zoophytes are faftened, have arrived at their full growth, and commonly contain the best pearls; but thofe that appear fmooth, contain either none, or fmall ones only.

Were a naturalift to make an excurfion for a few months to Manâr, the small island near Jafna and the adjacent coaft, he would discover many natural curiofities, ftill buried in obfcurity, or that have never been accurately described.

Indeed no place in the Eaft Indies abounds more with rare thells, than thefe for there they remain undisturbed, by being theltered from turbulent feas, and the fury of the furf. I will juft name a few of them, viz. Tellina joliaca Linn,* Tell, Spenglerii, Arca culculata,† Area Now, folen anatimus Linn. Oftrea Ijognomum, Terebullum, albi. dum, ftriatum, Turbo fcalaris† Bula volva Linn, Vexillum ingritarum, &c. Amongst the beautiful cone fhells: conus thalaffiarchus Anglicanus cullatus, § amadis thaiarchus con. generalcis Linn. c. capitaneus,** e. miles, tt c. fercus mufcarum, # c. reteaureum, c. glaucus,|||| c. cereola, regia corona murus lapedius, canda erminea focietas cordium. There

are many others, befides thofe already mentioned, equally valuable and curious.

The great fuccefs of the rev. doctor John, in conchology, when at Tutucorin, and affifted by G. Angelbeck, with a boat and divers: and the capital collections made by his agents, whom he afterwards fent there with the neceffary in ftructions and apparatus, may be feen in Chemnitz's elegant cabinet of fhells, in 4to. (with illuminated plates), and how many new fpecies of zoophytes he difcovered, we learn from another German work by Elper, at Erlangen, the third, volume of which is nearly finished.

fulphur; their figure is that of a rhomboidal octaedron, some of which are nearly an inch high, and are perhaps the fineft fpecimens of native volcanic fulphur yet known.

The fteam aifing from the vents appeared, from the taste and fome experiments, to be pure water.

The elevation of the peak above the fea being about 1900 toifes, induced me to make on its fummit feveral chymical experiments, in order to compare their refults with what takes place in our laboratories: it will be fufficient to give the results without encumbering the reader with the detail.

The volatilization of liqiuds and the confequent production of cold was very confiderable, a minute was fufficient for the evaporation of a full dofe of ether.

The action of acids on metals, earths, and alkalis, was flow, and the bubbles that escaped during the effervefcence were of a much greater fize than ufual. The production of vitriols was attended with fome fingular phenomena; that of iron became inftantly of a beautiful violet colour, and that of copper was fuddenly precipitated of a bright blue.

I examined the humidity of the atmosphere by means of the hygrometer, pure alkali, and fulphuric acid, and conclude, that during the abfence of clouds the air is very dry, for at the end of three hours the fulphuric acid had not undergone any change of colour, or gained any increafe of weight: the fixed alkali remained dry, except on the edges of the veffel, where it appeared to be a little damp; the index of the hygrometer pointed to 64 degrees, but we could not fix it with perfect exactness on account of the violence of the wind.

The

The smell and strength of liquids appeared to be not in the leaft impared by this height, contrary to the extraordinary accounts of fome even modern travellers: volatile alkali, ether, and spirit of wine, poffeffed their ufual pungency. The fuming liquor of Boyle was the only one that fuffered any perceptible lofs of ftrength; its evaporation, however, was not retarded, for in thirty feconds a fmall quantity that I poured out had difappeared, leaving behind only the fulphur, which gave a reddifh tinge to the fides and bottom of the veffel. On the addition of a little fulphuric acid to this liquor it detonated britkly, and the vapour that arofe had a fenfible degree of

heat.

I attempted to produce the volatile alkali by decompofing fal ammoniac hy fixed alkali, but its effect was flow, and hardly to be perceived, whereas on the fea fhore an equal quantity of materials produced it readily and in great abundance.

Defirous of alcertaining the nature of the vapours which were rifing from the crater, particularly, whether they contained any inflamma ble air, fixed air, or marine acid, I made the following experiments. Having expofed fome nitrous folution of filver on the edge of one of the vents, and fuffering it to remain above an hour amid the rifing vapours, I perceived no alteration in it, which clearly showed the abfence of marine acid: I then dropped in a little marine acid, and there enfued an immediate precipitation of corneous filver; but, inftead of being white, as is commonly the cafe, it was of a fine dark violet colour, which prefently became grey, affuming the form of little fealy cryf ials diftinguishable by the naked eye,

fuch as M. Sage observed. (Vid, Min. docim.) From fome experi ments that I have made on the precipitation of corneous filver in inflammable air, I am inclined to attribute its change of colour to the prefence of that fubftance. Lime-water, after an exposure of three hours on the fide of the crater, in the neighbourhood of one of the vents, exhibited no pellicle, but merely a few floating detatched threads; hence proving, that there is not only no exhalation of fixed air from the crater, but that the quantity of it contained in this elevated expofure is not equal to that of the lower atmosphere; inflammable and fulphureous vapours being the only ones that abound here.

The electricity of the atmosphere was pretty confiderable, for the electrometer of M. Sauffure, held in the hand about five feet from the furface, indicated three degrees of pofitive electricity, whereas on the ground it flowed only one and a half.

The violence of the wind hindered me from making any experiments. on boiling water upon the crater itfelf, but at the icy fountain it continued in a state of ebullition at 71° of Reaumur's thermometer, the mercury in the barometer being 19 inches, 1 line.

I met with fome new varities of volcanic fchörls.

1. A triple cryftal belonging to the clafs of octaedral unequal-fided prifms.

2. Black fehör in octaedral unequal-fided prifms, terminated by oppofite triedral fummits, the plans of which forms two large irregular heptaedrons and a small scalene triangle produced by the truncature of the upper angle,

A com

of le Vaillant's Natural Hiftory of the Birds of Africa.

HIS African bird is fimilar to

4. Terminated at one end like the fummit of the preceeding criftal, and at the other by a diedral pyramid, all the edges of which are bevelled.

5. Terminated at one end by a tetraedral fummit, and at the other by a heptaedral, compofed of an irregular pentagon in the centre, five trapezoids on the fides, and a fixth on one of the angles.

6. Terminated at one end by a pentaedral fummit, compofed of four pentagons furrounding a truncated rhomb; and at the other by a pentaedral fummit differing from the firft only in a triangular truncature of the edge of two of the trapezoids.

7. Black fchörl with a hexaedral prifm, terminated at one end by a heptaedral fummit, compofed of two irregular hexhagons, two irregular pentagons, and three trapezoids; and at the other end by a tetraedral fummit, the truncatures of which form; 1. Two great trapezoids and one rhomboid; 2. Two fmall regular trapezoids; and between the great and the fmall trapezoids three truncatures, the firft hexagonal, the fecond pentagonal, and the third a fcalene.

Account of the Corbiveau, an African Bird; tranflated from the French

body, his feet, and his claws: his middle claw is united as far as the first articulation, by a membrane, to the inner one; and the feathers on the lower part of his beak are turned upwards, and cover his noftrils: but he is unlike the raven in his back, in the length of his wings, and in his graduated tail.

This bird appears to occupy in part the Ipace which is difcoverable between the genus of the ravens and that of the vultures; though he refembles the former in a greater degree than the latter. He is fimilar to the African vultures which I have already defcribed, in the fize of his wings; which when spread are three inches longer than his tail; in his graduated tail; in the form of his beak, which is compreffed fideways, convex above, crooked and rounded; that is to fay, raifing itself like that of the caffree and oricou, its whole length, and then progreffively becoming crooked. Thefe particulars diftinguifh the corbiveau from all the fpecies of ravens hitherto defcribed; and if travellers in future fhould difcover birds very fimilar to this, they may always afcertain the corbiveau, by the white patch on the nape of his neck, which ftrongly contrafts with the gloffy black that conftitutes the reft of his plumage; except a white mark which feparates the fides of this white patch on the back of his neck, and encircles the neck. This ftripe, (cordon) in itself not

very

very apparent, is formed by a fingle row of white feathers, or halfwhite, of which the outer border is alone vifible. The throat is of a lefs decided black than the rest of the body, and the feathers which cover it are forked; the beards extending beyond the stems as if the points had been cut off; a very remarkable circumftance, and fuch as I have had an opportunity of obferving in very few birds.

The tail of the corbiveau, which is less than that of the great raven, and larger than that of the grey raven, is much graduated, and the feathers on the fides are very fhort; the feet are black, and fo is the beak, which however has a white end to it; the iris is brown, like a hazel-nut. The claws of the corbiveau, it is obfervable, are ftronger and more hooked than thole belonging to the generality of

ravens.

This defcription of the corbiveau fhews that this fpecies of raven, if I may fo call it, has fome refemblance in point of form to birds of prey. The following obfervations on their manners and mode of life will confirm the resemblance. Noify, voracious, daring, focial, and dirty, he refembles the raven in his tafte for carrion, which conftitutes the chief part of his food; and he frequently affembles in large and noify crowds. Thefe birds raife hoarfe and hollow cries, not unlike thofe of the raven; and which fingularly conform with its fhape and manners to the difgufting ideas which we entertain of favage animals, in general, from the aggregate of their repulfive and mournful characteritics. To the habits which I have just mentioned, the corbiveau joins a marked appetite for live prey; he

attacks and kills lambs and young antelopes, and devours them after having pulled out their eyes and tongue; he may be feen following troops of buffaloes, oxen, and horses, the rhinoceros, and even the elephant himself. The love of live flesh and the blood leads these birds to purfue fuch great quadrupeds, on whose backs they are frequently perched in great numbers. The corbiveau would be a dangerous and fatal bird of prey to these animals, if he poffeffed ftrength fufficient to kill them: but, unable to penetrate their ftrong and folid hides, he contents himfelf with plunging his beak into the foft parts of the body of the ani mal, and where the skin has been injured by the vermin who depofit their eggs there. If these quadrupeds then permit the corbiveau on their back, they really derive a benefit from his fanguinary instinct ; a benefit, which they receive with confiderable pleafure, in fuffering him to remove with the point of his beak the fanguineous larve; of which the number is fo confiderable on certain animals, that I have seen many perish from the extreme waste which they occafion.

The corbiveau flies with great ftrength, and raises himself very high by means of his long wings.He builds his neft in October, and conftructs it in thickets, or trees: the neft is large and hollow, compofed of boughs, and furnished in the infide with fofter materials. It lays four eggs, greenish, spotted

with brown.

The corbiveau is not a bird of paffage, but continues the whole year in the country where he was born. I have fee him in every part of my African travels, though in fome places more frequently than