These obstacles, it is hoped, the following contrivancè will do much to remove."

gases.

A glass tube from 6 to 12 inches in length, and from 2 to 5 lines wide, so as to be capable of holding from 2 to 6 drachms, is to be hermetically shut at one end, and bended a little below its middle, so as to form two branches, of which the shut branch will be somewhat shorter than the other, diverging from each other nearly at a right angle. The vertex of the tube should be widened on the concave side, and this done more toward the shut than the open branch, as is represented in Plate II. Fig. 3. The vertex A of the convex side of the curvature does not correspond with B, that of the concave side, but is beneath the shut branch.

The gas evolved from the mutual action of two bodies, of which at least one is a liquid, may be collected in the shut branch in the following manner. Let the tube be held in the hand by the open end, so that this be the highest, and the shut end the lowest part of the tube; then the liquid is to be poured in till it begins to ascend above the vertex. The shut extremity is now to be elevated as high as the open end, while the veritex is depressed, so as to be the lowest part of the tube. In this position the shut branch will remain full, the liquid within it being supported by the pressure of the atmosphere on the small portion of the fluid, that is above the vertex, in the open branch. If a solid body, of greater specific gravity than the liquid, be now introduced into the open end of the tube, it will fall down to the vertex, and any gas evolved from its surface will rise through the liquid, and be collected in the shut branch, while the liquid will ascend in that which is open. Owing to the vertex of the convex side being beneath the shut branch, while that of the concave is nearer the open one, the whole, or almost the whole of the gas evolved, from any bit of solid måtter resting on the most depending part of the curvature, will ascend into the shut branch. In this manner the gas is collected unmixed with common air, and if the experiment requires the ap plication of heat, the bent tube may be placed in a sand-bath; so that by means of such tubes, experiments may be performed on small quantities of gases, not only more economically, but, it is hoped, more accurately than is commonly done on larger quantities, with a more costly apparatus.

A bent tube of the form described, may be also used for discovering the quantity of gas absorbed by a liquid. For example, the quantity of oxygen absorbed from atmospheric air by a solution of the protosulphate of iron. The air being confined in the sealed branch, by the solution contained in the open one, will be exposed to the pressure of the column of liquid, and as the open end may be corked, the solution can absorb no other gas but that contained in the tube. The quantity absorbed may, be known by tying, at the commencement of the experiment, a waxed thread around the tube, at the boundary of the air and liquid.

Other gases may be absorbed by other liquids, in nearly the same manner; for instance, carbonic acid by milk of lime; only when any other gas than atmospheric air is introduced into the tube, the whole tube must be previously filled with water. The water in the open branch, with the exception of a small quantity sufficient to confine the gas, is then to be sucked out with a straw or small glass tube, and the milk of lime substituted for it..

A bent tube of a small size answers best for collecting gas; and one of a larger size for the absorption of gases.

If the experiment to be performed requires any considerable time, the curvature of the tube may be passed through a slit made in a thin board, the slit being of such length that the branches of the tube may rest upon the board at the extremities of the slit. Experiments may be going on, at the same time, in several tubes, placed in as many slits in the same board, which may be made to form part of a very convenient portable frame, for holding a number both of bent tubes for gases, and test tubes for precipitations.

14

Fig. 4. is the plan of a board which may be made of mahogony, 8 inches square, and of an inch thick. In it there are eight slits for bent tubes, and at one end it is pierced with eight holes for test tubes. This board forms the top of the frame. Another board of the same dimensions, parallel to the former, forms the sole; and these two boards are connected together, at the corners, by four small wooden pillars. The whole frame need not weigh more than eleven ounces. It may be placed on a table or shelf, and may be lifted from one place to another, loaded with all the tubes that it is intended to contain, without disturbing any of the processes going on in these.

The slits and holes should be numbered, and a register kept of the processes going on in each of the tubes, by which they are occupied.

It is hoped that bent tubes will be found useful to students at Universities, to travellers, and to those who cannot carry large, brittle, and expensive apparatus along with them.

To those who have not the means of purchasing expensive chemical apparatus, the bent tubes will recommend themselves by their cheapness; each of them superseding, for small experiments, a retort, a pneumatic trough, and a receiver.

In the laboratory of the chemist they will also be useful, by enabling him to perform experiments, in the small space of 8 or 9 inches square, which would have otherwise required 8 or 9 retorts, and as many receivers.

An addition may be made to these tubes, by which the quality of the gas evolved at any period of the experiment may be examined, without disturbing the process going on. An account of this improvement will be the subject of an early communication.

PAISLEY,

October 1823.

ART. VIII.-Account of the Earthquake which happened in Chili, on the 19th of November 1822 *.

I

CANNOT refuse myself the pleasure of writing to you by so good an opportunity as that which now offers itself, particularly as I heard that you wished to have an authentic account of the earthquake which has taken place at Chili. I have received my information from some very intelligent persons; but as they all seem to agree, I shall adhere more particularly to that given by a friend of mine, who has taken notes. The whole description would fill a volume; so that I shall select those observations from memory, which I think are unlikely to have been inserted in the public prints, and which I think will be most interesting to you.

On the night of the 19th November 1822, at Quintera, the usual sea-breeze had completely subsided about 8 o'clock P. M. ;

*Extracted from a letter which we have been favoured with a sight of.

the atmosphere was perfectly clear, and it was a lovely moonlight; no change was observed in the temperature. At 9h 30m the first shock was felt, and the precise moment is curiously ascertained, by all Roskil's chronometers having stopped precisely at the same time*. And by all accounts, which, of course, are vague, owing to the inaccuracy with which time is generally kept in that part of the world, the earthquake was felt at the same moment throughout Chili. During that night there were about seven principal shocks, and continual inferior ones; so that Mrs Graham (the author,) it is said, held her watch in her hand 45 minutes, with a glass of water on the ground near her, and the water was shaken as nearly as possible every 5 minutes. The earthquake was felt at Conception slightly, more severely at Copiapo and Coquimbo, and some say at Lima, but this I think very doubtful. Valparaiso, Quillota, and Casa Blanca, seem to have been the centre (if I may express it so); and when my friend left it, which was three weeks after the first shock, it was still continuing at intervals, I suppose about three times a-day. At Valparaiso the ravages are inconceivable, and upwards of 300 bodies have already been dug out, mostly children and soldiers, which, I believe, taking the difference of population into account, exceeds any thing yet heard of, even at the great earthquake in Syria. I forgot to mention that it was felt at Mendosa, a town on the eastern side of the Andes, in the line of Buenos Ayres, and for some little way on each side of that town; and every endeavour was made to discover if it had taken place at Juan Fernandez, but this has proved quite unsuccessful, there being no inhabitants on that island.

The water retired with great rapidity in the outset, so as to leave the launches dry opposite the Custom House; but the return was gradual, much to the satisfaction of the inhabitants, and against the prophecies of the priests, who expected to have been swallowed up by it. Mrs Graham, and all other authorities, seem to agree particularly on this head, that the whole line of coast has either risen, or the water has subsided nearly two

• This I conceive to be a mistake, as I have seen a memorandum attached to a chronometer, in the handwriting of that watchmaker, in these words, "Let down at the earthquake." Besides which, I should at once say the cause was inadequate to stop a number of watches at once,

feet, and that rocks have made their appearance above water, which before were never seen, even at the lowest tides.

The motion and direction of the shock was from NW. to SE., and fissures running parallel to one another in a NW. and SE. direction, from a few inches to two or three feet wide, were discovered after the earthquake, throughout the whole district, wherever it was felt. At Vina de la Mar, which, you recollect, a few miles from Valparaiso, cones from two to six feet high were thrown up of sea sand, of which the little valley is composed. No smell, gaseous exhalations, nor steam, have been taken notice of; we may therefore suppose that none existed at the time. The houses situated on the loose alluvial soil, and in the Almendral, a sort of suburb adjoining Valparaiso, were generally shaken down, while those built on the rock mostly weathered the shock. Mr George Coode's new house on the beach, which he took so much pains to found upon the rock, is a good deal rent, but not so much as those on the opposite side of the street, and Mr Hoseason's house is completely demolished. Every church in the place, also the Fort, and Governmenthouse, are totally ruined. At Santiago, the capital, the damage is inconsiderable, a few houses having suffered in the roofs. Quillota is reported to be completely in ruins: it stands on alluvial soil in the valley near the river of that name, and on a dead flat about seven leagues from the sea.

It is to be observed, that water placed in a tumbler on the ground during the principal shocks, which were undulatory, was not tremulously agitated, but, as it were, thrown up on the side of the glass like a wave. On the contrary, during the inferior shocks which are described as vibrating perpendicular to the general direction of the great convulsion, the water in the tumbler was observed to have a bubbling motion. The average duration of the shocks was about 30 seconds. Mercury was also made use of, and the same phenomena noticed.

As felt on board the ships in the bay, it is described as if the chain-cable had run out in an instant; but we have very unsatis factory accounts of the general effects on the ocean. Sounds like distant artillery were heard some days after the commencement of the earthquake, but were not taken notice of at the time. RIO DE JANEIRO, August 4. 1822.