another determination of the longitude of Rio Janeiro, and six series of circum-meridian altitudes of the sun for the latitude. It is unnecessary here to notice the observations at the Cape, or the Isle of France; the positions of these having been long since settled. The longitude of Shark's Bay may be calculated, independently of the timekeepers, by twenty-four series of distances from the sun to the moon. On shore, at this Bay, only two series of observations of the sun's altitude could be obtained; but the journals contain a great number of observations, made on board the vessel while at anchor, which would if necessary complete the determination of the latitude. The position of Agagna at the Marianne Islands, has been determined by twenty-three series of circum-meridian altitudes of the stars; and by twentytwo series of distances; the latitude of Fort Santa Cruz, in the harbour of St. Louis, may be deduced from nine series of circum-meridian altitudes of the stars; that of Goats' Island, from two series of the sun's.

At Owhyhee, the only one of the Sandwich Islands where Captain Freycinet remained long enough to make any astronomical observations, we fina three series of altitudes of the sun for the latitude, and fifty-six series of distances from the sun to the moon.

At Port Jackson in New Holland, our navigators have determined the altitude of the South pole, by ten different stars, and the longitude by ten series of distances of the moon from the sun.

The position of French Bay, at the Malouine Islands, will be ascertained by twelve series of circum-meridian altitudes of the sun, and five series of distances.

Finally, Monte-Video, at the mouth of the River Plate, has been determined by nineteen series of lunar distances, and eleven series of meridian altitudes of the sun.

The observers who participated in the labours of which we have as it were given a catalogue, under the immediate direction of Captain Freycinet, were Messrs. Duperrey, Railliard, Bérard, Fabré, Pellion, Dubaud, Guerin, La. marche, Labiche and Ferrand. It will be observed here, as in former instances, that the order in which we have placed the names is not the order of their rank, but has been solely directed by their greater or less participation in each class of observation, treated in each paragraph of the Report.

V. HYDROGRAPHY.

Captain Freycinet and the officers serving under him, employed themselves most zealously, during the continuance of the voyage, in hydrographical observations; their operations will complete our knowledge of several groups of islands of the Great Pacific, which notwithstanding their importance, had hitherto been very little attended to.

The operations of this kind began on the West Coast of New Holland, at Shark's Bay, a survey of which had been made by Captain Freycinet himself, during Captain Baudin's voyage, and which he now rendered more complete. This last survey led to the discovery of a sand-bank, whose position has been accurately laid down; the publication of it will be of consequence to the security of vessels frequenting the Bay.

In the passage of the Uranie from New Holland to Waigooe, several parts of the Coast of Timor, and of some small islands in its vicinity, were carefully laid down.

In passing between the Island of Booroo, and the Islands of Amboyna and Ceram, Captain Freycinet had occasion to verify the accuracy of the map of that strait which was taken during the voyage of Rear Admiral D'Entrecasteaux; several parts of it, of which that officer had no knowledge, were explored by the geographers of the Uranie. As he uniformly followed the same track, Captain Freycinet had an opportunity of determining the position of the islands, situated to the South of Gilolo, and to examine, to the North of the Isle of Rooib, a very dangerous Archipelago, which had not been previously visited by any navigator. When he came to Waigooe, Captain Freycinet had charts made of such portions of the North coast of that island, as D'Entrecasteaux had only seen in passing; his operations will also supply us with detailed charts of Manooaran, of Rawack, and of several portions of the Island of Ayoo.

It was, however, at the Mariannes Islands, one the principal points of rendezvous, that the most complete hydrographical labour of the voyage was executed. The Island of Guam, for instance, which is the principal of them, was surveyed in the most minute manner, in its whole circum

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ference in canoes and also the Island of Rota, and a considerable part of Tinian. When the labours of the officers of the Uranie are added to those of Laperouse, there only remains the northern-most small island, the position of which has not been determined by French navigators; but as that island was visited by Malespina, it follows that we now possess all the materials for an excellent chart of the Marianne Archipelago.

In the Archipelago of the Sandwich Islands, the hydrographical operations of the expedition have procured us charts of several very extensive portions of the coast, as well as plans of different harbours and anchoring grounds.

In the passage from the Sandwich Islands to Port Jackson, Captain Freycinet discovered to the east of Navigator's Archipelago, a small island, to which he gave the name of Rose Island; and the positions of several very diminutive islands, at a great distance from the great masses of land, were also determined during the same passage. These islands will henceforward be direction points for vessels which have to traverse the Pacific, and where they may, as it were, step by step, verify their longitudes.

On their return from New Holland into the South Atlantic, by the South of New Zealand, Captain Freycinet first verified the position of Campbell's Island; and subsequently that of several small islands, situated at the Southern extremity of the New Continent, such as Sant-Ildefonso, Diego-Ramirez, Barnevelt, Evoots, &c. The atlas also contains maps of several portions of the coast of Terra-del-Fuego.

The lamentable catastrophe, which put an end to the voyage of the Uranie at the Malouine Islands, did not at all interrupt the hydrographical labours of the expedition; these labours have procured us charts of the North and North-east Coast of the most Western of the Malouines, as well as plans of the three harbours which it contains.

Such is a summary view of the immense hydrographical operations, which were executed during the voyage of the Uranie. The greater part of the drawings are finished; we have examined them, as well as the original memoranda, which have served for their construction; and we feel fully warranted in expressing our conviction, that when published, this atlas, which will consist of from thirty to thirty-four plates, will bear comparison with the best works of the kind hitherto published.

In terminating this article, we must not forget to notice, that almost the whole of this beautiful hydrographical labour has been executed by M. Duperrey. This able officer was assisted in some points by MM. Labiche and Bérard; the latter gentleman, also made drawings of some particular places at the Marianne Islands.

VI. METEOROLOGY.

We can scarcely hope, in our climate, to arrive at any general result upon the whole system of meteorological phenomena, otherwise than by the application of means properly combined from a long series of observations. At the equator, however, the changes are so rare, and so trifling, that a week almost is sufficient not only to perceive, but to measure the effects of constantly operating causes; in forty-eight hours for instance, the daily period of the barometer may be ascertained, and five or six days taken at random will enable us to appreciate its extent. At Paris the averages of a month will not always make that period clear, and it is very doubtful if the fortuitous effects of accidental causes are completely balanced, in the averages of two or three year's observations. There was, therefore, reason to hope that the short residence, which Captain Freycinet had to make at each of his points of rendezvous, would be quite sufficient to resolve several important ques tions relative to the meteorology of the equinoctial regions.

Our information on this subject has been considerably increased of late years; and we are in a great degree indebted for it to the labours of two members of this Academy. It still however remained to be ascertained by accurate measurement, if, in the daily barometical period of which we have just spoken, the hours of the maxima and the minima, between the tropics, are the same, in all seasons, and in all places; and also, if the oscillation of the mercury in the tube of the barometer is everywhere of the same extent, and in that case, what is its exact amount. Several naturalists have supposed that the mean pressure of the atmosphere is sensibly less at the equator, than in our climates. It may seem at first matter of surprise, to hear of any doubt being expressed on the subject; but when we consider how easily barometers are deranged; how difficult it is to find two that

perfectly agree, either from the faulty position of the figures on the scale, from the makers in general making no allowance for the effects of capillarity, or finally (what is most common of all) that the instruments are not equally well freed from air; it is easy to conceive how seldom opportunities have occurred of comparing the mean heights of the barometer under the tropics, and in Europe, so as not to apprehend, for instance, in the result, an error of one-fiftieth of an inch.

To be certain that these questions, and others which we abstain from here enumerating, have been completely solved in the observations which Captain Freycinet has brought us, would have required a complete discussion of them; the examination we have made of them, however, authorises us in saying that they will be of great use to the science. The preceding remark applies to the observations on shore. The nautical journals of the expedition present us, for the whole period of the voyage, with observations on the thermometer and hygrometer made hourly, both day and night; with observations on the barometer at every interval of two hours; and twelve daily observations on the temperature of the sea, taken at the same period. Such a mass of observations would under any circumstances be of great value; and we ought to add that the labours of Captain Freycinet and his assistants are not less remarkable for their accuracy than their numbers.

The very interesting memoir of Dr. Marcet, which was inserted in one of the last volumes of the Philosophical Transactions, would lead to an inference that the water of the ocean is salter south of the equator than in the northern hemisphere; the same inference is also to be drawn from the numerous observations of Baily made during Captain Cook's third voyage; inferences exactly opposite however are drawn from the specific gravities determined by Mr. Davy in his voyage from London to Ceylon. This point therefore required fresh examination; Captain Freycinet has within these few days sent to one of us fifty-five bottles of sea-water, collected at different anchorages to the north and south of the equator; these bottles have been most carefully corked, and we have every reason for believing that their examination will procure several new and interesting determinations to science.

This is perhaps the place to speak of the effects of the still which accompanied the expedition for the purpose of procuring fresh water, by the dis