is in a metallic or calcined ftate: by hammering, fome phlogifton may be transferred from the brafs to the iron; and in the fire, it may be abforbed again from the iron by the brass. To afcertain this point, he introduced fome calx of iron into minute cavities in pieces of naturally unmagnetic brafs, and found-that hammering did not produce magnetifm in this cafe, but that fire did; the reverfe of what happens to the magnetic brafs. He therefore thinks it demonftrated, as far as the fubject will admit of demonftration, that the magnetism acquired by brass is not owing to iron contained in it. It must be obferved, however, that the objection fuppofes the iron to be diffused through the brafs, in a state of intimate, or chemical union; whereas, in the experiments, the iron was diftinct, having no degree of union with the brafs; circumstances obviously very different. This infufficiency of the above experiments feems to have been pointed out to the Author by Dr. Blagden; for the Poftfcript is followed by a letter to that gentleman, giving an account of an experiment made plainly in confequence of fuch a remark. A very fmall portion of iron was united by fufion with unmagnetic brafs, which thereby became very weakly magnetic, every part of its furface juft fenfibly attracting one end of the needle; and this weak degree of magnetifm was neither increased by hammering, nor annihilated by foftening. This experiment appears conclufive; and yet the conclufion drawn from it seems to be rather weakened by fome obfervations which the Author has fubjoined: he found that naturally magnetic brafs loft its power of acquiring magnetifm by being melted partially, and recovered it again by being fairly melted; and that a long continuance of a heat juft below fufion generally dimi nishes, and fometimes quite deftroys that property. 'The needle employed in thefe experiments deferves notice, on account both of the fimplicity of its construction, and its having been found much more fenfible than the best of those now in ufe. It is fufpended by a chain, confifting of five or fix circular Jinks of horse hair, each link about three quarters of an inch in diameter, and the ends of each of the pieces of hair joined by a knot and fecured with a little fealing wax. The upper link is hung on a pin, and a piece of fine filver wire, about 1 inch long, hooked to the lower. The lower end of the wire goes round a fmall cylindrical bit of cork, through which a common fewing needle, made magnetic, is thruft horizontally. links, on account of the fmoothness and lightness of the hair, move freely on each other, and allow the needle more than a whole revolution round its center, with fo fmall a degree of friction, that it may be confidered as next to nothing. The NATURAL NATURAL HISTORY. Particulars of the prefent State of Mount Vefuvius; with the Account of a Journey into the Province of Abruzzo, and a Voyage to the Ifland of Ponza. By Sir William Hamilton, K. B. F. R. S. The many curious particulars contained in this paper will not admit of an abftract. The Author obferves, upon the whole, that the more opportunities he has of examining this volcanic country, the more he is convinced, that volcanoes fhould be confidered in a creative rather than a destructive light. Many new discoveries have been made of late, particularly in the South Seas, of iflands, which owe their birth to volcanic explosions ; and fome, where the volcanic fire ftill operates. It is probable, that on further examination, most of the elevated islands at a confiderable distance from continents would be found to have a volcanic origin; as the low and flat islands appear, in general, to have been formed of the fpoils of marine productions. -Vefuvius, the Solfarerra, and the high volcanic ground on which great part of Naples is built, were once probably islands, and the Author conceives the iflands of Procita, Ifchia, Ventotiene, Palmarole, Ponza, and Zannone, to be the outline of a new portion of land, intended by nature to be added to the neighbouring continent: the Lipari iflands, all of which are volcanic, are looked upon in the fame light with respect to a future addition of territory to the ifland of Sicily. This paper is accompanied with three plates; one, a plan of the island of Ponza; the other two, views of rocks of lava and bafaltes upon the island. An Account of a Subfidence of the Ground near Folkflone, on the Coaft of Kent. In a Letter from the Rev. John Lyon, M. A. to Edward King, Efq. With Remarks by Mr. King. In No. 349 of the Phil. Tranfact. (for the year 1716) there is an account, by the Rev. Mr. Sackette, of an uncommon finking of the earth in the fame neighbourhood, which is there attributed to the hills or cliffs, which confift of great ragged fandftones, ftanding on a wet bottom of flippery clay, having flidden forwards, towards the fea, as a fhip is launched upon tallowed planks. The fubfidence defcribed in the prefent Paper happened in September 1785, and is accounted for fomewhat differently, viz. from the foundation being undermined by waterdrains, which abound in the loofe marley bottom: the ground now resembles an arch that has funk down, and which has left its two abutments, a hill and a cliff, standing; and the preffure of the hill, being more than a counter-balance to that of the finking ground, upon the ftratum of wet marle, has forced upwards tome rocks, at the diftance of a few yards, and squeezed the wet marle in many places up with them. The fituations of the parts in which the alteration has taken place, and of the adjacent country, are reprefented in two plates. 8 Conjectures Conjectures relative to the Petrifactions found in St. Peter's Mountain, near Maeftricht. Bv Petrus Camper, M. D. F. R. S. A great number of petrified bones of various kinds, particularly large jaw-bones with their teeth, were discovered in this mountain, about the year 1770. They were fuppofed by naturalifts to be bones of the crocodile. Dr. Camper has here refuted that opinion, and fhewn, from the great quantity of undoubted marine productions found along with them, that they belonged rather to marine than river animals, and from a comparison of their structure and conformation with the real bones of crocodiles, that they could not have belonged to that animal; but, on the contrary, have the effential characters of the Amphibia Nantes. The defcriptions are illuftrated by two plates. Account of fame minute British Shells, either not duly obferved, or totally unnoticed by Authors. By the Rev. John Lightfoot, M.A. F.R.S. A nautilus lacustris, a helix fontana, a helix spinulosa, and turbo helicinus, two land fhells, and a patella oblonga, found on the leaves of the water-flag, are defcribed, and different views of them exhibited in three plates. They were all discovered, as the Author informs us, by Mr. Agnew, gardener to the late Duchefs dowager of Portland, and by his faithful pencil they were drawn. After the account of thefe fhells, Mr. Lightfoot takes notice of an error which has been almoft univerfally adopted by the collectors and dealers in fhells, refpecting certain fubjects brought from the West Indies, and commonly known by the name of gold Shells. They are yellow gloffy fubftances, of the size of tares or vetches, compofed of brittle imbricated fcales, like the foliaceous buds of a tree, generally with a perforation in fome part. By macerating thefe fuppofed fhells in hot water for a few minutes, and then carefully developing the fcales, he found an infect in the center, of a roundifh figure, about the fize of a small bedbug, and in every inftance except one (out of at least fifty that were opened) without wings. The fingle fpecimen that had wings was oblong, and narrower than the reft, as in the other infects that are winged and unwinged in the different fexes. From the whole of this curious examination it appears, that the gold fhells are no other than the cafes or cells of an infect in its pupa ftate, and that the infect is a fpecies of cochineal or coccus, probably not hitherto described. Account of a new electrical Fish. new electrical Fish. By Lieutenant William Paterfon of the 98th Regiment. While the regiment was at the Ifland of Johanna, one of the Comora iflands, in its way to the Eaft Indies, the Lieutenant caught two of these fishes in a linen bag, and fufficiently afcertains their electric faculty. He gives a drawing (acknowledged to be but an imperfect one) and fhort defcription of the fish, fuch as circumftances would admit. It appears to be different in in many refpects from the electric ones hitherto defcribed; about 7 inches long, 2 broad, with a long projecting mouth; the back dark brown, the belly fea-green, the fides yellow, the fins and tail of a fandy green; the body interfperfed with red, green, and white spots. We mention thefe particulars, as our Review may come into the hands of those who may have opportunities of making further enquiries. Particulars relative to the Nature and Customs of the Indians of North America. By Richard M'Caufland, Surgeon to the King's, or eighth Regiment of Foot. The Indians of America have been faid to differ from other males of the human species, in the want of a beard; and as the Esquimaux are found to be furnished with that usual characteriftic of the fex, they are fuppofed to have had an origin different from that of the other natives of America. Inferences have hence been drawn, refpecting not only the origin, but the conformation, of Indians; and philofophers are obliged to Mr. M'Caufland for undeceiving them in regard to the matter of fact. He has produced decifive evidence, that the Indians do not differ from the rest of men in this particular more than one European does from another; that they pluck out the hairs on their first appearance, and continue the fame practice when any appear afterwards, having an inftrument on purpofe for that ufe; and that many of them allow tufts of hair to grow on particular parts of the face, refembling thofe we fee in different nations of the old world. A few particulars are fubjoined refpecting the Six Nations; their divifion into tribes, the fucceffion to the dignity of Sachem, and the inftitution of private friendships: when any one is killed, it is the duty of every furviving friend to replace him to the family, either by a fcalp, a prifoner, or a belt of fome thousands of wampum. New Experiments on the ocular Spectra of Light and Colours. By Robert Waring Darwin, M. D. When any bright object has been long and attentively looked at, an image, or refemblance of that object, remains fome time vifible after the eyes are turned away or fhut. This appearance in the eye Dr. Darwin calls the ocular spectrum of that object. Thefe fpectra the Doctor divides into four diftinct kinds: ft, Such as are owing to a lefs fenfibility of a defined part of the retina, which he terms Spectra from defect of fenfibility. 2dly, Such as are owing to a greater fenfibility of a defined part of the retina, or spectra from excess of fenfibility. 3dly, Such as refemble their object in colour as well as form, or direct spectra; and 4thly, Such as are of a colour contrary to that of their object, or reverfe fpectra. From confidering the first clafs our Author concludes, that the retina is not fo eafily excited into action by lefs irritation after having been lately fubjected to greater.' Every nerve in the 6 the human body obferves the fame law; and we know not any membrane, whofe furface is fenfible, that can be irritated by a lefs action immediately after having fuffered a greater. The conclufion drawn from the fecond clafs is the reverse of the foregoing, namely, that the retina is more eafily excited into action by greater irritation after having been lately fubjected to a lefs. The direct spectra prove, in Dr. D.'s opinion, that a quantity of ftimulus, fomewhat greater than natural, excites the retina into fpafmodic action.' The 4th clafs induces our Author to conclude, that the retina, after having been excited into action by a ftimulus fomewhat greater than the laft, falls into oppofite fpafmodic action.' Such are the general inferences that the Doctor draws from the experiments here recorded; but the experiments themselves, which are really curious, cannot be abridged without exceeding our bounds. We therefore refer our readers to the Tranfactions at large. The reader will, however, find fome inconvenience from the plates being uncoloured; for which reason we would advife him to make coloured drawings of each figure on feparate papers, which will enable him to repeat thefe pleafing experiments with greater accuracy. We have always fuppofed that, during vifion, the eye, efpecially the retina, was in a paffive ftate; but from these experiments of our ingenious Author, all vifion feems to be owing to the action of this organ: It is even probable that the retina is furnished with mufcular fibres. An Investigation of the Caufe of that indiftinctness of Vision which has been afcribed to the fmallness of the optic Pencil. By Dr. Herschel. In this paper the Doctor relates a number of experiments which tend to prove, that the fmallness of the optic pencil has not fo great an effect in rendering vifion indiftinct, as has been generally imagined. He concludes with wifhing that, till he has repeated, extended, and varied thefe experimental investigations, they may be confidered as mere hints that may afford matter for future difquifitions to the theoretical optician. At prefent the Doctor's engagement in conftructing a forty-feet reflecting telescope (amazing undertaking!) fcarcely permits much leifure for other purfuits. ART. II. The Bhagvat-Geeta, or Dialogues of Kreefhna and Arjoon. Tranflated from the Original, In eighteen Lectures, with Notes. in the Sanfkreet, or ancient Language of the Brahmans. By Charles Wilkins, Senior Merchant in the Service of the Honourable the East India Company, on their Bengal Etablishment. 4to. 7s. 6d. Boards. Nourfe. N the various and interefting hiftory of the human mind, our curiofity is irrefiftibly attracted by thofe pages, which exhi bit manners and opinions far removed from our own. To fuch defcriptions |