ART. III. Description of the Apparatus, alluded to in the foregoing Paper, for bringing up Water from certain depths in the Sea.

A is the bottle. B is a cylinder 12 inches long, and 1 in internal diameter; it is open below, but made tight above by a screw; a piston works in this tube, and at common atmospheric pressure includes a space of 6 inches between its internal surface and the top of the tube. A rod passes downwards from the under surface of the piston to the length of about 5 inches, and is then connected with the piece C by a

cross bar, passing through the aperture D, so that C is in fact a prolongation of the piston rod; and as D is an opening in the tube which extends nearly half way up it, a motion of the piston and the affixed part is allowed to that extent. E is an arm sliding freely upon the cylinder. F is a screw fixed into it, which steadies, but does not bind the piece C. G is a click, or small lever, which is pressed by the bent spring on the outside against the edge of C, and catches in the notches, when any one of them comes opposite to it. H is a small inclined plane which acts on the lower arm of the lever G. I is a piece which may be fixed on any part of C by the thumb screw, and when sufficiently raised, it comes in contact with the socket of the arm E. K is a lever attached to the plug of the cock; there is a spiral spring fixed round it at the head of the bottle, which constantly tends to throw it up and open the orifice. L is a second click or lever, which is pressed by a spring towards a horizontal position; its lower arm catches on a pin projecting from the end of the lever K, and keeps it down, the other end moves against the edge of the arm E. The cylinder is retained firmly in its place by two pieces passing from the top and bottom of the bottle. There is a square-headed screw in the bottom of the bottle, which, when removed, lets out the water: and the whole is slung in gimbles, to which the rope is made fast.-The action of the apparatus is as follows:-When the piston rises in the cylinder, it elevates the rod and the piece I; this coming against the socket of E, lifts the whole arm, and the inclined edge above acting on the end of the lever L, sets it off from the notch of the arm K, which rising, the bottle is opened, and water may enter. When the piston falls again, the click G catches in a notch on the edge of C, (these notches being made at proper intervals) and the arm E is in consequence brought down by means of the pin in its upper end; it depresses the lever K, and brings it within the click L, so that it is again retained in its first position; and the moment this is done, the parts are so adapted to each other, that the inclined plane H, presses upon the end of the click G, and when it has descended a very little further, C is entirely liberated from the notch in which

If the

it had caught, and the arm E is left unattached. piston descends lower, it carries the piece C down with it, but does not affect any other part.-When the parts are adjusted to each other, a scale is marked off on C, the various points of which coincide with one, two, three, and more atmospheres; and the piece I being set at these points, liberates the lever K at the moment those pressures are obtained; so that the whole being thrown into water, as it sinks, the pressure of the column of water above is exerted on the piston, and opens the bottle at the precise depth for which the piece I had been previously set.

The instrument was made under the direction of Sir. H, Davy, by Mr. Newman of Lisle-street.

ART. IV. Extract of a Letter from John Davy, M. D. te Sir H. Davy.

Trincomale, Oct. 3, 1817.

My different excursions have been highly interesting. As soon as possible I shall give you a pretty minute account of the results of my observations. Now I must be very concise indeed. In July I went to the southern part of the island, and visited the districts of Matura and the Malagan-patton.In the former, gems abound. I saw the natives at work in search of them in alluvial ground. Here I ascertained that the native rock of the sapphire, ruby, cat's eye, and the different varieties of the zircon, is gneiss. These minerals and cinnamon stone occur imbedded in this rock. In one place I found a great mass of rock, consisting almost entirely of zircon in a crystalline state, and deserving the name of the zircon rock. It is only a few miles distant from a rock called the cinnamon-stone rock, from its being chiefly composed of this mineral, in company with a little quartz and adularia. In the Malagan-patton, the most re. markable phenomena, and what I went chiefly to see, are the salt-lakes, the nature of which hitherto has been considered very mysterious, from the want of inquiry, which I was

able to make in a very short time, and ascertain the source of the salt. Many of these lakes are of great extent, and in a great measure formed by an embankment of sand thrown up by a heavy sea, along a level shore. The water that falls in torrents during the rainy season, is thus confined, and inundates a great part of the country; the sea, more or less, breaks over or percolates through the sand-banks, and thus the water is rendered brackish.-In the dry season the wind is very strong, and dry, and the air very hot; it was from 85° to 90° when I was there. The consequence is a very rapid evaporation of the water-the drying of the shallow lakes.and the formation of salt. It is from these lakes chiefly that the island is supplied with salt. The revenue that this one article brings Government, amounts to about £10,000 annually. The Malagan-patton altogether is a singular country; its woods, and it is almost all wooded, are principally composed of euphorbia and mimosæ :-its few inhabitants are a sickly race, miasmata destroying their health, and the wild animals, with which the country abounds, as elephants, hogs, deer of different kinds, leopards, bears, &c. destroying the fruits of their labour. In the beginning of January I attended the Governor and Lady Brownrigg to Kandy, and had a good opportunity of becoming acquainted with the manners of the natives. The country in the interior, and particularly round Kandy, is magnificent: its grand features are high hills and mountains, and deep valleys, and perpetual wood, and perennial verdure ;-the wood is in faulty excess. The climate is fine; the air cool; generally at night below 75°; averaging all the year round the moderate temperature of 74°. From Kandy I made an excursion alone into Dombera, and explored a mountainous region, where a white man was never seen before. My object was to examine a cave that yields nitre. It is a magnificent one in the side of a mountain, in the depths of a forest surrounded by mountains of great height and noble form. I shall send you a particular account of this, and of other nitre caves I have visited. The rock is a mixture of quartz, felspar, mica, and talc, impregnated near the surface with nitre, nitrate of lime, and sulphate of mag

nesia, and in one spot with alum, and in another incrusted with hydralite, similar to that round the Geyser, in Iceland. From the mountains of Dombera I looked down on the wooded plains of Birtanna, and saw the great lake of Birtanna, which no European I believe ever before visited; it is full of alligators. Returning to Kandy, after a short stay there I next came to this place, through a country almost entirely overrun with wood-three days we travelled in a noble forest without seeing a single habitation. I wish you could see some of the noble ebony trees which flourish here, and without observing any traces of cultivation; but some fine remains of antiquity, especially about Candely lake, indicating that the country had once been in a very different state.

ART. V. Translation of a Letter from a learned Foreigner to a Friend in this Country, on the Figure of the Earth, and on the Length of the Seconds Pendulum in different Latitudes.

AT the present moment, when the philosophers of France Ат

and England are conjointly engaged in attempts to determine, with the utmost precision, the length of the seconds pendulum in different latitudes, and the measure of the earth, you have thought that it would be not uninteresting to point out in a simple and popular manner, the exact object of these operations; what means are made use of in their execution; and lastly, what useful results are likely to be derived from them to science and society. Such is the object of the letter which I have the honour to address to you.

Although these questions ought naturally to be discussed in the order in which they are proposed above, which is regulated by their mutual dependence, it may perhaps be adviseable first to touch slightly upon the latter, and to indicate what of great and profitable, such researches may have for the human mind. Those who are specially engaged in the cultivation of the