observation. It is highly desirable, in many points of view, that its existence should be substantiated, and the limits of the phenomenon both - along the coast and in the ocean, ascertained by further evidence. Its effects upon the copper sheathing of ships cannot fail to be highly injurious, and a question of still higher interest even arises, whether this deleterious gas may not contribute to the well-known unhealthiness of the coasts from which these waters are taken.

"Upon searching for evidence of a similar phenomenon having been observed before, I have found in the Philosophical Transactions, for 1819, a memoir by the late Dr. MARCET," on the specific gravity and temperature of sea-waters, in different parts of the ocean, and in particular seas, with some account of their saline contents." Out of sixteen specimens which he examined, he found one which was brought by Captain HALL, from the Yellow Sea, in the Chinese Ocean, which, from the account which he has given, must probably have been as highly charged with sulphuretted hydrogen, as those which I have just examined from the coast of Africa; and he observes, there is something in the develop. ment of sulphur in sea-water, which is by no means well understood.'

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"If the existence of this curious phenomenon should be confirmed, the origin of the sulphuretted hydrogen will probably be found to be the same as that of the same gas in various saline lakes in different parts of the world, from which Trona or Natron is derived. The mud of the Lonar Lake in India, of a lake near Maracaybo, in South America, and of similar lakes on the north of Africa, are all found to be thus impregnated. The sulphuretted hydrogen thus adhering to the clay, has been supposed to be derived from volcanic sources, but Mr. MALCOLMSON, in an able memoir lately printed in the Geological Transactions, says, that he has observed the same phenomenon in the salt water inlets, along the Indian coast, wherever the bottom contained argillaceous and carbonaceous matter;' and he ascribes the effect to the decomposition of the sulphates in the water by the carbon, and the clay only prevents its passing off into the air, or mixing with the water by the power of adhesion.'

"The subject is full of interest, both in a practical and scientific point of view, and well worthy of further investigation.

"I am, &c.,

J. F. DANIELL.”

"KING'S COLLEGE, 20TH AUGUST, 1840. "SIR,-I have carefully examined three sheets of copper taken from the bottom of the Bonetta, and have now the honor to report as follows:"Numbers one and two were pretty uniformly covered on the outside with a green crust; and on the inside, as evenly, with a black crust of equal thickness. They were very thin in parts, and partly eaten into holes.

"Number three was in a much worse state, very thin and eaten into large holes. In most parts it was easily broken by the fingers; one of the holes, of an irregular shape, measured eighteen inches in length by four inches and a half in width. This sheet was covered with green crust chiefly on both sides; but there were evident traces of the black crust on the inner side.

"Upon analysis the black crust was found to consist of sulphuret of copper, and the green of subchloride of copper.

"Connecting these results with those previously obtained from the analysis of the waters on the coast of Africa, I have no doubt that the injury to the copper has arisen, primarily, from the sulphuretted hydrogen.

"I am, &c.,

J. F. DANIELL."

"It is impossible not to speculate upon the origin of the deleteriou gas, which has now been proved to impregnate the waters upon the we tern coast of Africa, in such enormous quantities, through an extent d more than sixteen degrees of latitude. The supposition that it may have been generated by the spontaneous change of any of the contents of the water after it was sealed up in the bottles, may be set aside by the slight est consideration.

"It appears to me, that there are only two sources to which it can with any probability be referred, namely, submarine volcanic action, in which case its evolution might be considered direct or primary; and the reaction of vegetable matter upon the saline contents of the water, in which case it would be secondary.

"The probability of a volcanie origin is, I think, small, from the absence, I believe, of any other indications of volcanic action, and from the great extent of the coast along which it has been traced.

"What is known of the action of vegetable matter upon the sulphates, and the immense quantities of vegetable matter which must be brought by the rivers within the influence of the saline matters of the sea, renders, on the contrary, the second origin extremely probable. Decaying vegetable matter abstracts the oxygen from sulphate of soda, and a sulphuret of sodium is formed. This again acting upon water, decomposes it and sulphuretted hydrogen is one of the products of the decomposition. You will perceive that there is a large proportion of the sulphates in the different specimens of water which have been analyzed, and there can be little doubt, I imagine, that extensive mud banks must be formed at the mouths of most of the rivers on the western coast of Africa, within the tropics, consisting chiefly of vegetable detritus in the exact state which is most favorable to the action which I have described. This view rests upon experimental evidence, and upon considerations of great cogency, derived from the unhealthiness of certain well known situations in which decaying matters from tropical vegetation are brought into contact with sea-water. I feel more than ever convinced, that the evolution of the sulphuretted hydrogen is intimately connected with the unhealthiness of such stations. "When this matter was first brought under my consideration, I was surprised that the nauseous smell which must necessarily be evolved from water impregnated with this gas, at so high a temperature as that of the equinoctial regions, had not been noticed. I have, in consequence, turned to some of the accounts of the late travels in Africa, to seek for evidence upon the subject; and in the Narrative of an Expedition into Africa, by MACGREGOR LAIRD, I found the following important observa

tion:

"The principal predisposing causes of the awful mortality were, in my opinion, the sudden change from the open sea to a narrow and winding river, the want of the sea breeze, and the prevalence of the deadly miasma, to which we were nightly exposed from the surrounding swamps. The horrid sickening stench of this miasma must be experienced to be conceived: no description of it can convey to the mind the wetched sensation that is felt for sometime before and after daybreak. In those accursed swamps, one is oppressed not only bodily but mentally with an indiscribable feeling of heaviness, langor, nausea, and disgust, which requires a considerable effort to shake off.'

"Now these observations were made in the very locality from which some of the first waters, which I examined, were taken, and nothing more is wanting to identify the cause of the rapid decay of the ship's copper with that of the mortality of the climate.

"It has been experimentally found, that so small a mixture as a fifteen hundredth part of sulphuretted hydrogen in the atmosphere, acts as a direct poison upon small animals, and the sensations of langor and nausea, described by Mr. LAIRD, are exactly those which have been experienced by persons who have been exposed to the deleterious influence [of this gas] in small quantities.

"The peculiar unhealthiness of mangrove swamps in all parts of the world, I have little doubt, arises from that tree requiring salt water for its growth, and its decaying foliage being thus brought into immediate contact with the sulphates. The hypothesis also agrees with the fact, (which I believe has been established,) that the unhealthiness of such situations does not extend to any considerable distance from the sea.

"The commanders and other officers of expeditions for exploring the coasts of Africa, should be directed to bestow particular attention upon the subject, and, at all events, not to linger in situations where the water affords indications of the noxious gas. I am, &c., "J. F. DANIELL."

"It will be remarked in the above reports, that in no case was sulphu retted hydrogen found in the water taken up in any of the rivers; in fact, as Professor DANIELL has shown, it is only generated in salt water. The obvious bearing of this upon the Niger Expeditionis in the gratifying fact that twenty miles inside the river (which is the limit of the mangroves and the salt water,) they may have nothing to fear from this deleterious gas, which probably aggravates, if it does not originate, disease; unless it should happen that the south-west wind should carry the miasma to some distance with it-that such should be the case is very probablebut as three or four days, at the most, would suffice to steam through the Delta, there is not much risk to be encountered, and there can be little doubt but that the malaria will be effectually stopped by the barrier of high mountains which extends in an east and west direction across the river, above Damuggoo, and before reaching Attah. In the extract given above from LAIRD and OLDFIELD's Narrative, &c., it must be remembered that the first sickness and death in that expedition began at Cape Coast Castle; three died before entering the river, and the great mortality took place before they reached Damuggoo at the extreme upper end of the Delta, where they only arrived after a voyage of thirty-six days, from the 11th of October to the 16th of November, or twenty-seven from their entrance of the river Nun.

"Now it must not be forgotten that just before entering the river, in 'breaking out' the hold to lighten the vessel, it was discovered that the cause of a 'disagreeable vapor, from which they had long suffered, was, that the bags containing the cocoa had rotted, and the cocoa had fallen into the salt bilge-water and there become putrid.' Here, then, were the very ingredients for generating sulphuretted hydrogen to a great extent; the lamentable consequence has been before alluded to, namely, three deaths before reaching the river. After this, for a short time, no case of sickness occurred till some distance below Damuggoo, when it broke out with redoubled fury, and the Quorra lost thirteen men, the Alburkah only two; evidently the cause was in a great measure to be found on board. Mr. LAIRD acknowledges that certainly the Quorra was by far the more un healthy of the two vessels.'

"The latitude of this deadly spot is 5° 54'. Now, upon referring to Captain W. ALLEN's chart of the Quorra, it will be seen that this position is exactly at the southern foot or to seaward of a range of hills; in like

manner Damuggoo, or Adah-mugu, of the same chart, lies to the southward or to seaward of the great chain of mountains above alluded to. And we venture to express an opinion-we might almost say convictionthat owing to these mountains forming the barrier to the passage of the malaria, it is probable that miasma will be found accumulated at such spots; and that wherever predisposing causes exist on board, it is in these places that sickness will be most severe.

"It is hardly necessary to add, that the confluence of the Quorra and Chadda― the supposed head quarters of the Niger Expedition-is nearly 100 miles beyond these spots, and to the northward of the high range of mountains; and no cause has yet been shown for supposing that it may not prove as healthy there as in other tropical climates.

"Should there be no cause for delay at Ibu-and we earnestly trust that there may not be there seems no reason why two, if not all. the steamers of the Niger Expedition should not pass Damuggoo and reach Attah within seven days after entering the Quorra."

ABYSSINIA.

THE same work contains an extract from a letter written in Upper Abyssinia, a part of which we copy.

The writer seems to be an English agent, ostensibly employed in scientific investigation, but whose more important business is to ascertain such facts as may be interesting to the British, in view of extending their commercial operations.

The points of possession which Great Britain is gaining on either side of the Red Sea, will be of great importance in connexion with her East India commerce. Should she succeed in extending her influence over Abyssinia, we hope she will pursue a less objectionable policy than that which has marked her course in India.

"TAJURRAH, 22D NOVEMBER, 1840.

"This being the point at which my journey into the interior of Africa may be properly said to begin, I have now the pleasure to commence a regular correspondence with you, which, God willing, I shall continue at every fitting opportunity.

"Leaving England on the 1st September, I arrived at Alexandria on the 19th, and, after six weeks' detention in Egypt, quitted Suez, by the Berenice steamer, on the 1st November, arrived at 'Aden on the 10th instant, where I was most favorably received by Captain HAINES, the Political Agent.

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'A boat being on the point of sailing for this coast, I left 'Aden on the 12th, and arrived here on the 15th instant.

"I was kindly furnished by Captain HAINES with letters to the Sheikh or Sultan of Tajurrah, MOHAMMED ibn MOHAMMED, and also to MOHAMMED 'ALI, who belongs to a tribe of the Danakil in the interior, and who is the constituted guide of all travellers to Shoa. On my arrival, he immediately came on board, and conducted me to the Sultan, by whom I was received very favorably.

"I have engaged to accompany me, as a servant and interpreter, HusSEIN, a young man, who has been from his childhood with the Missionaries of the Church Missionary Society in Tigre and Cairo, and who was with Mr. KIELMAIER at the time of his death, at Kidelu, in April last. He speaks the Arabic, Dankali, and Amharie languages, and having been aceustomed to the Society of Franks, is able to make himself very useful to me.

"The Political Agent at 'Aden has entered into alliance with the Somali and Dankali tribes, and purchased two islands at the entrance of Tajurrah Bay, as also a small one at the upper end, immediately at the entrance to the inner bay. The French have purchased settlements within the Red Sea, at Edd and Amphila, at about 150 and 200 miles distance, respectively, from the entrance of the Strait of Bab-el-Mandeb, on the western or Abyssinian shore.

"Captain HAINES has also directed a survey of the coast from Bab-elMandeb to Berbera, and the E. I. C. brig Euphrates is at present employed thereon, having completed as far southward as Zeila', where that vessel now is. This survey extends as far into the interior as the salt lake Asal; and I shall do my best to lay down my route correctly from that point to Ankobar. But, owing to the war now carrying on, as I am told, between the Dankali and the people of Argobba, a country in the neighborhood of the river Hawash, and tributary to the King of Shoa, or Sultan of Ifat, as he is here called, the road is now closed, and it is uncertain how long I may be detained here.

*

“Tajurrah is inhabited by persons of the different Dankali tribes spread over the country between the coast and the Hawash. MOHAMMED 'ALI, for instance, is the son of the Sheikh of a tribe located at Harrar. The Danakil, who continue to lead a nomadic life, carry up salt from the lake to the west of Tajurrah; in return for which they bring from Ifat nothing but horses, for which that country is celebrated. But the traders of Tajurrah, who import manufactured goods, metals, tobacco, pepper, &c., from the ports of the Arabian coast, bring down from the interior, in exchange for the same, slaves, ivory, coffee, &c. The particulars of this trade, I shall know better hereafter; but thus much seems quite certain, that the principal article of export is MAN. I am very careful not to give rise to suspicion by any marked inquiries. I shall, please God, be long enough in these countries, and have sufficient intercourse with the natives, to enable me to obtain all the necessary information, and by seeming to employ myself solely with scientific matters, I hope the readier to gain their confidence.

"My daily walks have served to make me tolerably well acquainted with the character of the country in the immediate vicinity of Tajurrah. The village is situate in an alluvial plain, on the north side of the bay, at the foot of a mass of low hills, which range from south to north, and are intersected by valleys, which, in the rainy season, bring down the waters from the interior. From the debris contained in these valleys, and the plain which they have formed, it is manifest that they communicate with a country of primative formation; but the hills in the immediate vicinity of Tajurrah, as far as I have inspected them, are entirely composed of madrepores, and other marine products, which at a comparatively recent period, have been elevated from the sea. That this neighborhood has been the stage of violent volcanic action is manifest from the trap rocks which overlie and intersect these cretaceous hills, and by which those parts of them in immediate contact have been converted into chalk. This chalk, where exposed,