ration of the different alcoholic solutions, a red and apparently fatty matter was obtained. This matter has no smell, or sensible taste; is insoluble in cold or boiling water, but soluble in sulphuric ether, and pure cold alcohol. This solution is of a scarlet colour. It is not disturbed by the addition of distilled water, which shews that it is not of a fatty nature. Its natural colour is not changed by potash, soda or ammonia. The mineral acids have no action upon it, when diluted with water; but, when concentrated, they destroy it, by changing it to a dirty yellow. The salts of lead, tin, iron, and copper, do not precipitate this colouring matter from an alcoholic solution diluted with water.-Journ. de Pharmacie, tom. vi. p. 174,-175.

34. On the colouring matter of the membrane which lines the shell of the Crab.-M. Lassaigne also examined the membrane, which, in young crabs, adheres strongly to the shell, but which may be easily separated from it in large crabs. It is extremely fine, and of a violet colour by reflected light, and a purple violet by transmitted light. When put in water it does not lose its colour; but in cold alcohol it gives out a great quantity of red colouring matter, similar to that which is extracted from the shell. Though treated successively with several doses of alcohol this membrane retains a little of its red violet colour, which cannot be taken away from it by other solvents without destroying the membrane itself. The colouring matter has the same properties as that of the shell.

M. Lassaigne has found the same principle in the shells of lobsters, and other animals of the same order, and he concludes,

1. That crabs, &c. contain a red colouring principle, which may be extracted by means of cold alcohol.

2. That this colour is not formed by the action of heat, but that it is developed or distributed in the shell by the impulsion of that fluid.

3. That there exists a highly coloured membrane, which appears to be the source of the colouring matter in that class of animals; and,

4. That this colouring matter differs in its chemical properties from others obtained from the mineral and vegetable kingdom. -See Journ. de Pharm. tom. vi. p. 175, 176.

35. On the Alloys of Potassium and Sodium, with other metals.The following are the results deduced by M. Serullas from the elaborate memoir which we have already had occasion to quote, (see page 389.)

1. That very fusible metals, treated in a high temperature with tartrate of potash or soda, are susceptible of producing alloys more or less rich in potassium or sodium, and which may, without being decomposed, resist a very strong fire.

2. That the existence of potassium and sodium in these alloys manifests itself, 1. By the more or less vigorous action which they exert upon water; 2. By the rotation of their fragments in a bath of dry or wet mercury; 3. By the solidification of the mercury which is agitated with them; 4. By the considerable quantity of caloric which they emit, when they are pulverized or exposed to air; 3. That the pyrophorus owes its property of burning in contact with the air to the presence of a certain quantity of potassium.

4. That not only the tartrates, but also the salts whose base is potash or soda, decomposable by heat, are brought to the state of potassium and sodium by means of the charcoal, which is either added or naturally contained in the vegetable acids which form a part of the salts; and that this reduction is singularly favoured, as M. Vauquelin first remarked, by the presence of metals, of which several then join themselves to the potassium or sodium.

5. That the antimony of commerce proceeding from arsenical mines of this metal contains often arsenic, in consequence of the resistance which this last appears to bring to its solidification when it makes part of an alloy.-See Journal de Pharmacie, Dec. 1820, tom. vi. p. 589.

36. Dobereiner on the chemical action of Capillary Tubes.M. Dobereiner is of opinion, that chemical combinations and decombinations may be effected by simple capillarity, and he has succeeded in producing sugar, by uniting the carbonic acid and carbonated hydrogen, by the aid of charcoal and compres sion. Experiments of this kind are very dangerous. A strong tube of copper, filled with charcoal, and in which M. Dobereiner had introduced two gases by compression, burst with a tremendous explosion. Annal. Generales des Sciences Physiques, tom. vi. ch. xi

37. Existence of Alcohol in Pyrolignous Acid.-In examining the pyrolignous acid obtained from birch, M. Dobereiner found alcohol in it. Some time after, a manufacturer of salts wrote him from Moscow, that in rectifying wood vinegar, he had collected about a third of brandy. In dissolving large masses of lead in wood vinegar, alcoholic vapours have been observed in such quantities as to deserve being condensed and collected.-Ibid.

III. GENERAL SCIENCE.

38. Mr Campbell's second Journey in Africa.—The Reverend John Campbell, a native of Edinburgh, who published, some years ago, an account of his travels in the South of Africa, has revisited that part of the world, and penetrated much farther than he did formerly. Upon arriving at Leetakoo, the limit of his former journey, and about 900 miles from Cape Town, he found that the inhabitants had removed to a new settlement, called New Leetakoo. Proceeding N. E. for more than 100 miles, he passed through two towns, one of which, Masheu, contained from 12,000 to 15,000 inhabitants, and where much land was under cultivation. Thence he proceeded still farther to the NE. for more than 100 miles, and reached Kurrechane, the chief town of the Marootze tribe, containing about 16,000 inhabitants, who have many founderies, and smelt iron and copper ores from the neighbouring mountains. They excel in making baskets, and ornament their walls with paintings of elephants, camelopards, shields, &c. Kurrechane is supposed to be in 26° of S. ́Lat. and not very distant from the eastern coast. Some of the

rivers flowed W., and others E. or SS. E. Several large towns are said to be to the east of Kurrechane, and Mr Campbell saw the smoke of one or two of them. He was allowed to send Missionaries to Kurrechane with the promise of protection.— Lond. Journ. of Science and the Arts, vol. ii. p. 72*.

39. Destruction of the village of Stron.—The village of Stron, in the district of Fermian in Bohemia, was situated a league

• We have just seen a copper bracelet of very curious workmanship, which Mr Campbell brought from the interior of Africa, which shews their knowledge of the working of metals. - ED.

above the Saatz on a declivity, partly in the vicinity of the Eger, and partly in a gorge which descended to that river. This hill was formed of a sort of earthy coal, covered with a bed of sand and alluvia. On the upper part of the declivity were several springs, which lost themselves in the small but rugged hills of moving sands upon the banks of the Eger, which flowed at the distance of about 400 yards from the village. These springs appear to have excavated large subterranean hollows, so that the church, the houses and the gardens, rested only on pillars as it were, which became weaker and weaker every day. For some time back, the grand bed appeared to sink in several places; but in the month of February a great noise was heard at midnight; the inhabitants felt that the earth was decending; and they found next morning, that half of the village had disappeared, and had fallen to a considerable distance from the place which it occupied. The hill and the church, indeed, had almost wholly disappeared, and at some distance there was a mass of debris, from which the roof and the chimneys only ap peared. The church is now eighty feet below the place on which it was built. It is divided into two parts, one of which is burned, and the spire overturned: only one-fifteenth part of the houses now remain, and even these are not in a state of security. The Eger appears to have undermined, by degrees, the supports of the whole of the hill, which were very much inclined in front.-Gilbert's Annalen der Physik, 1820.

40. Weight of the Dutch Pound Troy.-In a paper read before the Literary and Antiquarian Society of Perth, on the weight of the Dutch Troy pound, Mr Anderson demonstrated, that the original weight of that pound had been 7680 grains. After stating the theoretical investigation by which he arrived at this result, Mr A. remarked, that it was strongly confirmed by an examination which he entered into some time before, with the view of determining the weight of the Scotch pound, from the various multiples and subdivisions of that weight, in the possession of the Guildry of Perth.

This set of weights, he stated to have been presented by Government to the Guildry of Perth at the time of the Union, and to be uncommonly accurate from the ounce to the stone, throughVOL. IV. NO. 8. APRIL 1821.

Ff

out all its denominations, never deviating above one-tenth of a grain from what it ought to have been, on the supposition of the pound being 7680 grains. There was another confirmatory circumstance. By James I. it was enacted, that the pint should contain 41 oz. Trone weight, of the clear water of Tay; and by James VI., that the same measure should contain 55 oz. Scotch Troy of the water of Leith. If the water enjoined in the two cases had been the same, the pound Trone would have been to the pound Scotch Troy as 55 to 41; but the specific gravity of the water of Tay being to that of Leith as 100 to 103 nearly, it is a curious circumstance, that if this be taken into account, and the pound Scotch Troy reckoned 7680 grains, the pound Trone will turn out exactly 10,000 grains Troy.

41. Black Resinous Varnish used at Silhet in Bengal.-This black varnish, celebrated for its lustre and durability, is prepared in the following manner: the nuts of the Semecarpus Anacardium, and berries of the Holigarna longifolia, having been steeped a month in clear water, are cut transversely and pressed in a mill. The expressed juice is kept for several months, and the scum taken off from time to tinre. The liquor is then decanted, and two parts of the one are added to one part of the other, to be used as varnish. Other preparations are sometimes employed, but the juice of the Semecarpus always predominates. The varnish is laid on like paint, and is polished by rubbing it when dry, with an agate or smooth pebble.-Quart. Journ. vol. x. p. 315, 316.

42. Manufacture of Catgut Strings.-The catgut strings used for harps and violins, are manufactured at Whitechapel, &c. of the peritoneal covering of the intestines of the sheep; but have always been considered inferior to those exported from Italy. Dr MacCulloch ascribes this superiority to the leanness of the Italian sheep,-it is known, that the membranes of lean animals are stronger than those of fat ones; and he suggests, that the catgut should be manufactured from the Welch Highland or Southdown breeds, in preference to those which, like the Lincoln, are prone to excessive accumulations of fat.-Quart. Journ. vol. x. p. 267.

43. On the Selection of Ice for Ice-houses.-M. Hemptinne of Brussels has shewn, that ice for summer use should be taken from the river on a very cold day, and be exposed on the following