BOTANY.-Though the number of plants is fo confiderable, be ing estimated at about twenty thoufand, that the most retentive memory can scarcely remember their names, the ardour for this branch of fcience does not feem to decrease.

La Billardiere, who went round the world with d'Entrecafteaux, brought back with him a valuable collection in every part of natur al history. His herbal is most beautiful; and though nearly one fourth of it has been loft, he has still about three thousand plants, of which from twelve to fifteen hundred are new.

He carried with him from the Friendly Ifles twenty-two breadfruit-trees, twelve of which were left at the Ifle de France. Of the eight brought to France, five died; two have been fent to Cayenne; and the other was brought to Paris, where it is now in the Jardin des Plantes.

La Billardiere brought with him alfo about three hundred birds, a third of which almoft are unknown. His collection of infects has been much damaged; but he has ftill a great many in fufficient prefervation to be defcribed. Riché, who went on the fame expedition, brought with him à variety of objects, and particularly birds. He died not long ago.

Michau has returned from South America, and brought with him a great number of plants in excellent prefervation. He will no doubt foon publish an account of them, as well as of those which he brought from Perfia.

Coloumb having ordered fome poplars to be cut down in the fpring time, obferved, that when the axe approached the centre of the tree a very large quantity of air was difengaged, but that none was difengaged when the inftrument attacked the other parts of the tree. It is well known that the medullary parts, in which the air circulates particularly, is fituated towards the centre. From this medullary part proceed thofe tranfverfal veffels which extend to the bark of the tree for the circulation of the air. The plant contains alfo other veffels for the circulation of the fap and of all the vegeta ble juices. There are also glands where the fecretion of all thefe different liquors is performed to produce the propolis pollen, &c. A vegetable, therefore, in the fimpleft cafe, may be confidered as an affemblage of feveral pliable elastic fibres, compofing a great number of veffels of different calibres, in which water, air, and various kinds of fluids drawn from the bofom of the earth and the atmosphere, circulate.

Light also has a great influence on vegetation. Humboldt has fhown that the light of a lamp may, in this refpect, fupply that of the fun; and that plants which receive the light of a lamp are coloured green, as if they received that of the fun. Excefs of light hurts plants, especially when they begin to rise.

According to Ingenhouz, plants fuffer oxygen to be difengaged in the light, and the carbonic acid in darknefs. Senebier is of opin

ion that the latter changes the oxygen into the carbonic acid, by furnishing it with carbon.

Humboldt has obferved that mushrooms furnish hydrogenous gas in the day, as well as the night-time.

MEDICINE. The carbonate of barytes and pure cauftic barytic earth are most active poifons. Pelletier killed several dogs by mak ing them take from twelve to eighteen grains of these substances.

Mankind have been long employed in attempting to discover means for the prolongation of life. Valli, after laying down prin ciples well known, viz. that old age comes on naturally, because the calcareous phosphate or calcareous carbonate is continually ac cumulating in the greater part of the folids, fuch as the bones, the arteries, veins, tendons, &c. fays, that this accumulation can be guarded against only two ways; either by preventing that fubftance from being formed in the mafs of the fluids, or by expelling it as foon as it is formed.

1. To prevent too abundant a production of that earth, one must ufe aliments which contain the least quantity of it, fuch as vegetables, milk, fifh (but fifhes contain a great deal of the phosphoric acid.)

2. The means which he thinks moft proper for expelling that calcareous earth, or calcareous phosphate, are, bathing, frictions, duretics, pure water, and beverages cooled with ice. In fhort, he confiders the oxalic acid given in fmall dofes as the best remedy. That acid, fays he, decompofes the calcareous phosphate: the oxalate of lime which thence results will be carried into the torrent of circulation, and will be driven outwards.

Vauquelin and Brogniard have proved that the acetic acid diffolves the vegetable glutten and the animal fibres. It is well known that there is a difeafe called by nofologifts malacofleon, or mollities offium, where the bones become entirely foft. The calcareous phosphate is almoft entirely carried away, and there fcarcely remains any thing but the cellular tissue of the bones, with the gelatinous and greafy part, or the marrow. Were it poffible to find out the means of diffolving, gradually, in this manner the calcareous phosphate, without depriving the bones of their folidity, and without hurting the other animal functions, the fountain of youth would be discovered. It appears therefore that it may not be altogether impoffible to retard age at leaft.

PHYSIOLOGY.-Spallanzani having deftroyed the eyes of bats and fet them at liberty in an apartment, obferved that they could guide themfelves from one place to another as before. They avoided every obftacle that was prefented to them, and even passed through rings which he placed before them: and for this reafon he afks, "May not these animals poffefs a fenfe with which we are not acquainted, and which may fupply that of fight? or, May not Emell be fufficient for that purpofe?".

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Jurine is of opinion that it is hearing which fupplies the above want. He filled with wax one of the ears of those animals which he had deprived of fight and he obferved that they flew about with difficulty: when he filled both their ears, they could not fly at all. METEOROLOGY.-Meteorology, which depends only on an immense number of obfervations, has, however, been exalted into a fcience. It affords general refults of great importance; a collection of which has been made by Cotte. By thefe it appears that the barometer varies very little under the equator. Its variation be comes greater in proportion as it approaches the poles. It feems to experience a diurnal and an annual variation.

Diurnal variation.-Between the hours of ten and two, both of the day and the night, the rifings and fallings of the mercury are the leaft. The contrary takes place between the hours of fix and ten of the morning and evening. This feems to depend on the fun and the moon paffing the zenith.

Annual variation.-The ofcillations are lefs in fummer, greater in winter, and very great at the equinoxes. This feems to depend like the tides and the winds, on the fame action of the fun and the

moon.

Thermometers. The mean degrees of heat are almost the fame in all latitudes. Kirwan has given a table for calculating the mean degrees of heat in different latitudes.

Rains are more frequent in winter than in fummer; more abun, dant in fummer than in winter. Mean quantity of rain at Paris twenty-two inches. The evaporation generally exceeds the rain at Paris. The mean evaporation is thirty-three inches,

Aurora borealis is more frequent about the time of the equinoxes than at any other feafon. This phenomenon is almost continual in winter in the polar regions. For fome years past it seems in our climates to have become lefs frequent.

Lunar period of nineteen years. It appears that the general tem perature of a year returns the fame every nineteen years, an epoch when the phases and position of the moon, in regard to the earth, are alfo the fame. From the above period, therefore, we may prediet, very nearly, the temperature of any given year. This method is practifed by the makers of almanacks; and their predictions, to a certain degree, may be depended on. This mode of calculation is well known alfo to merchants who fpeculate in the price of provifions.

Maurice at Geneva makes meteorological obfervations of the utmost importance, because he has thermometers placed at different heights above the surface of the earth, as Pictet had formerly, and others at the depth of four feet below it. He gives an acount, therefore, of the evaporation of the earth, electricity, humidity, &c. His obfervations appear every month in an excellent collection, published by the brothers Pictet, under the title of Bibliotheque Brit annique. It appears that the thermometer, which is four feet below

the earth, ftands generally between 9° and 10° Reaum. (52° and 54° Fahr.) and that it experiences very little variation.

ZOOLOGY.-Great attention has been paid to the natural history of animals. Cuvir has published a number of memoirs on Zoology, and fome have been published alfo by Geoffroy. Daubenton proposes to divide the animal kingdom into eight claffes:-1ft, vivipa rous quadrupeds, of which he reckons 415; 2d, cetaceous animals 15; 3d, birds 2,424; all these animals have two ventricles in the heart: 4th, oviparous quadrupeds, of which he reckons 113; 5th, ferpents 175; 6th, fishes 866; all these animals have only one ven tricle in the heart, and their blood is almoft cold; 7th, infects, of which he reckons 15,000; their heart is of different forms; their blood is white; they have trachea, and breathe by ftigmata; 8th, worms, of which he reckons 1,159; their heart is of different forms, their blood is white, and they have no apparent entrance for the air.

Cuvier and Geoffrey have made feveral interesting researches in regard to that class of animals called mammalia. The former, in a memoir on the rhinoceros, has proved that the two kinds known by Camper, viz. that of Afia and that of Africa, may have one, two, or three horns. The horns, therefore, cannot be a characterifing mark to distinguish them. The diftinguishing mark, howev. er, of the African rhinoceros is, that it has only twenty-eight dentes molares, while that of Afia has twenty-eight molares and fix incifores. He is of opinion alfo, that there are at least two other fpecies in exiftence, and perhaps a third.

Camper has proved alfo, that the African elephant is different from that of Afia. The teeth of the latter are composed of tranf verfal zones, and thofe of the African elephant represent on their furface a kind of trefoils or lozenges. It appears, that befides thefe two species there exift two others, and perhaps three. Swediaur fays, that the greater part of the elephants' tuiks used in commerce are collected in the immense pastures of Africa, where these animals feed, and that the negroes fet fire to the meadows in order to difcover them.

Audibert propofes to give a history of apes. He has already published one number, containing fix coloured plates, folio fize.

Birds. Le Vaillant has already published a part of his Natural Hiftory of the Birds of Africa, confifting of five numbers, each containing fix coloured plates, in folio and quarto. He has announced that the whole work will contain 600 plates. An edition in twelves, with fome plates, will appear alfo. The two first volumes will be published without delay. He propofes to give a complete history of birds.

Fifbes.-Bloch has published the laft fix volumes of his beautiful work on fishes. They contain, like the former fix, 216 plates, on feveral of which are reprefented from two to three subjects He has been obliged to make feveral new genera. This is one of the most beautiful works that ever appeared on ichthyology.

Lacepede is preparing a large work on the fame fubject. He has fhewn that the anableps, a fifh hitherto believed to have had four eyes, has in reality only two; but each of its eyes has two cornea, two cavities for the aqueous humour, two irides, two pupils, but only one cryftalline humour. Different naturalifts have published feparate memoirs on fome particular kinds of fish, and their differ ént parts. Herbft has published at Berlin a very beautiful work on crabs, with coloured plates.

Infects. This part of natural hiftory is become almost as im menfe as botany. Brogniard continues his fuperb collection of the butterflies of Europe. Fabricius has given a new edition of his Entomologia Syftematica, emendata et auda. Latreille has publifhed his Genera of Infects, and D'Anthoine has publifhed an excellent memoir on the cynips (gall infect) of the oak. Bofc has defcribed fome other fpecies of the cynips, and Luce has described a phofphorefent beetle, found near De Graffe.

Panzer is now publishing a work on the infects of Germany, entitled Fauna Infe&orum Germania, printed at Nuremberg. He has published alfo a history of the infects of America. Raeufchel has printed a work at Leipfic, entitled Nomenclator Entomologicus emendatus. Hedwig has given a new edition of the Fauna fiftens, Infecta, by Roffi; in which are defcribed the infects found in the neighborhood of Florence and Pafa. Martin has published the Infects of England. This work, like that on fhells, is executed in a masterly manner.

Polypiers.-There are certain fubftances which are neither animals nor vegetables, called polypiers; fuch as coral, corallines, madrepores, &c. Girod Chantram has carefully examined some of thefe fubftances, which had hitherto been claffed among the cryptogamia kind of plants: fuch as the byffus, conferva, ulva, tremella, &c.; and obferved, that the greater part of them are compofed of tubes or veffels, in which beings that appear to be animated circulate. He even distinguished in one fpecies of conferva a real volvox, which had some fimilarity to the rotator of Gmelin.

These fuppofed plants, by a chemical analyfis, give the fame refults as animal fubftances. He therefore concludes that they are not plants, but fpecies of polypiers, formed, like coral, by small animals. Of thefe polypiers he diftinguishes two kinds; fome without tubes, and fome which have tubes. We fhall then have three orders of polypiers: 1ft, The calcareous, fuch as corals and madrepores; the fubftance of which is hard and calcareous :—2d, Corallines, the fubftance of which is foft and flexible, like fponge :-3d, The conferve, the fubftance of which is abfolutely herbaceous. It is to be wifhed that naturalifts would pay attention to the study of the infects which construct these different kinds of polypiers, as they are ftill unknown.

SENSIBILITY OF PLANTS. The caufe of this fenfibility is ftill little known. The following is the explanation given of it by