ion, and the illumination of the wood, is produced; and he at the fame time thinks, that this procefs cannot proceed in the irrefpirable kinds of gaffes, Rotten wood alfo, in which the ne ceffary quantity of hydrogen and carbon is not at the fame time difengaged, does not obtain the property of illuminating. Mr. CORRADORI, however, objects to this theory, that the flow combustion does not take place according to the above theory, as the wood, at the time when it begins to illuminate, is mostly deprived of its refinous particles, and confequently contains but very little hydrogen and carbon; and it appears to him more probable, that the more it lofes of combuftible matter, the more it obtains the property of illuminating. There is, in fhort, he thinks, a very great difference between this natural and the artificial phosphorus. Mr. HUMBOLDT concludes from his experiments, that the illumi-" nation of rotten wood takes place only when it gets in contact with oxygen; and when it has loft the property of emitting light in irrefpirable gaffes, it recovers it again by expofing it to oxygengas. Dr. GARTNER, however, is of opinion that according to his experiments, a certain degree of humidity is always requifite; and he thinks, that oxygen gas is not quite neceffary, though the illumination is increafed by it. This phenomenon, however, be ing fo very different from all known proceffes of combuftion, where light is difengaged, Dr. Gartner afks whether it is not more agreeing with the animal procefs of refpiration, than with a true combustion, or whether the illumination of the wood is produced by phosphorus and carbon in a proportion hitherto unknown. Dr. Gartner is, on the whole, inclined to think, that it is at prefent impoffible to give a fatisfactory explanation of the all phenomena that occur in this procefs. Mr. BoECKMANN has made numerous obfervations and experiments on the illumination of rotten wood, in different gaffes and fluids, in order to throw fome light on the ideas of the above naturalifts. The refults of thefe experiments differ in fome points from what the experiment of thofe gentlemen have fhewn, which, however, Mr. Boeckmann afcribes to the nature of rotten wood, as a fubftance that is not always of the fame kind, and has not always an equal degree of putrefaction and humidity. It feems to differ likewife materially from the artificial phofphorus by the following diagnostics. 1. It fhines in oxygen gas at a very low temperature. 2. It emits light in all irrefpirable gaffes, at leaft for a fhort time. 3. In muriatic gas its light is fuddenly extinguifhed. 4. It fhines in a lefs degree in air, rarified by the air pump. 5. According to Mr. Corradori, it even fhines in the toricellian vacuum. Its illumination is extinguished in oxygen gas, as well as in other kinds of gaffes, when they are heated. 7. By its illumination in oxygen gas, carbonic gas is produced. 8. One may fuffer the rotten wood to be extinguifhed feveral times, one after another, in irrefpirable gaffes, without depriving them of the property of making new pieces of rotten wood fhine again. 9. Humidity

6.

greatly promotes the illumination, and feems even to be neceffary in producing it. 10. The rotten wood continues to fhine under water, oil, and other fluidities, and in fome of them its light is even increased. All this feems to fhew, that the extinction of rotten wood, in different media, does not immediately depend on a want of oxygen, but rather on a particular change, to which the wood itfelf has been exposed.

ON THE EFFECTS OF OXYGEN IN ACCELERATING GERMINATION.

MR. HUMBOLT difcovered, in 1793, that fimple metallic

fubftances are unfavourable to the germination of plants, and that metallic oxydes favour it in proportion to their degrees of oxydation. This discovery induced him to fearch for a substance with which oxygen might be fo weakly combined as to be eafily separated, and he made choice of oxygenated muriatic acidgas mixed with water. Creffes (lepidium fativum) in the oxygenated muriatic acid fhewed germs at the end of fix hours, and in common water at the end of 32 hours. The action of the first fluid on the vegetable fibres is announced by an enormous quantity of air bubbles which cover the feeds, a phenomenon not exhib→ ited by water till at the end of from 30 to 45 minutes. These experiments announced in Humboldt's Flora Subterranea Fribergenfis, and in his Aphorifms on the chemical phyfiology of Plants, have been repeated by others.* They were made at a temperature of from 12 to 15 Reaumur. In the fummer of 1796, Humboldt began a new feries of experiments, and found that by joining the ftimulus of caloric to that of oxygen he was enabled still more to accelerate the progrefs of vegetation. He took the feeds of garden creffes (lepidium fativium,) peas (pifum fativum,) French beans (phofeolus vulgaris,) garden lettuce (laduca fativa,) mignonette (refeda odoratà;) equal quantities of which were thrown into pure water and the oxygenated muriatic acid at a temperature of 88° F. Creffes exhibited germs in three hours in the oxygenated muriatic acid, while none were feen in water till the end of 26 hours. In the muriatic nitric † or fulphuric acid, pure or

*See Uflar's Fragments of Phythology, Plenck's Phyfiology, Villdenow's Dendrology, and Didionnaire de Phyfique par Gehler

The nitric acid, however, diluted with a great deal of water, accelerates germination alfo, according to the experiments of Candolle, a young naturalift, who has applied with great fuccess to vegetable phyfiology. This phenomenon is the more interesting, as chemistry affords other analogies of the oxygenated muriatic acid and the nitric acid. Profeffor Pfafs, at Kiel, by pursuing Humboldt's experiments, has found that frogs fuffocated in oxygenated muriatic acid gas increase in irratability, while those which perish in carbonic acid gas are lefs fenfible of Galvanism.

.

mixed with water, there was no germ at all: the oxygen feemed there to be intimately united with bafes of azot or fulphur, to be difengaged by the affinities presented by the fibres of the vege table. The author announces that his discoveries may one day be of great benefit in the cultivation of plants. His experiments have been repeated with great industry and zeal by feveral diftinguished philofophers. Profeffor Pohl at Drefden caused to germinate in oxygenated muriatic acid the feed of a new kind of euphorbia taken from Bocconi's collection of dried plants; 110 or 120 years old. Jacquin and Vander Schott at Vienna threw into oxygenated muriatic acid all the old feeds which had been kept 20 or 30 years at the botanical garden, every attempt to produce vegetation in which had been fruitlefs, and the greater part of them were stimulated with fuccefs. Even the hardest feeds yielded to this agent. Among thofe which germinated were the yellow bonduc or nickar tree (guilandina bonduc,) the pigeon cytifus or pigeon pea (cytifus cajan,) the dodonea anguftifolia, the elimbing mimofa (mimefa fcandens,) and new kinds of the homea. There are now fhewn at Vienna very valuable plants which are entirely owing to the oxygenated muriatic acid, and which are at present from five to eight inches in height. Humboldt caufed to germinate the clufia rofea, the feeds of which had been brought from the Bahama iflands by Boofe, and which before had refifted every effort to make them vegetate. For this purpofe he employed a new procefs, which feems likely to be much eafter for gardeners who have not an opportunity of procuring the oxygenated muriatic acid: He formed a pafte by mixing the feeds with the black oxyde of manganefe,, and then poured over it the muriatic acid diluted with water. Three cubic inches of water were mixed with half a cubic inch of the muriatic acid. The veffel which contains this mixture maft be covered but not clofely fhut: elfe it might readily burft. At the temperature of 95° the muriatic acid becomes ftrongly oxydated; the oxygenated muriatic gas which is difengaged paffes through the feeds; and it is during this paffage that irritation of the vegetable fibres takes place.

HISTORY OF ASTRONOMY, FOR THE YEAR 1800, By JEROME DE LELANDE, Delivered on his Entrance into the French College.

HE laft century has produced many remarkable events in aftronomy: telescopes indeed and Kepler's laws and attraction will place it before every other. Nothing was before achiev ed, and the century when aftronomers began to labour should be that of discoveries. We have been furnished with twelve memora ble epochs,-A new and principal planet, eight fattellites discovered, the return of comets known and demonftrated, with fixty-eight new comets obferved; the aberration and nutation of the stars,

*

Venus's tranfit, with the precife diftance of the fun and all the planets; the form of the earth with its irregularities; calculations as to inequalities produced by attraction, and principally with refpect to Jupiter and Saturn, which have afforded correct tables of each planet, and its fatellite; lunar tables, the most important, fo precife as to ascertain its motion within a quarter of a minute; and laftly 50,000 ftars observed: to these may be added, improvements on aftronomical inftruments: fectors, meridian telescopes, whole circles, reflecting circles, Short's and Herfchel's telescopes, compenfation-balances, and marine time keepers, all of which have affumed a new face during the last century.

The conclufion of the last century was remarkable on many accounts. Some days before the conclufion of 1799, C. Mechain made the discovery of a comet in Ophiuchus; Meffier likewife obferved it. Mechain and Burckhardt took an early opportunity of calculating its elements.

What was deemed difficult fifty years fince, is now but the labor of a few hours. This comet was only perceivable for a few days, and to the naked eye appeared as a ftar of the fifth or fixth magni tude. This makes the gift whofe orbits have been calculated. Its calculation was alfo made in Germany by M.Olbers & M.De.Wahl.

The arduous labour with regard to the stars, which commenced August 5, 1789, has been vigorously continued and happily terminated by Le Français Lalande. He has determined the places of 50,000 stars, from the pole to two or three degrees below the tropic of Capricorn; and with Burckhardt has conimenced a review of the zodiacal conftellations, in the hope of discovering some new planets. Madame Le Français having reduced 10,000 stars, has commenced the reduction of the whole number with unexampled fpirit.

The clofe of the century has also been particularly distinguished by the theory of the moon.

June the 13th Laplace made known a new refult of the theory, which is a nutation of the lunar orbit, the refult of the earth's ob late form. By this inequality we may infer, that the lunar orbit, inftead of moving with a conftant inclination to the ecliptic, moves in a plane, and paffes the equinoxes between the equator and ecliptic, inclining to the latter at an angle of fix or feven feconds. He finds alfo an inequality of the moon, depending on the longi tude of the node, which is fix feconds.

The course of the moon for 1002 years was attended with a difficulty now removed. The obfervations of the Arabians in the 10th century were of the greatest importance in this respect.

The Inftitute propofed, as the fubject of a prize, the compari 'fon of numerous obfervations of the moon, with the tables to fix the epochs of the lunar longitude, of the apogeum and the node. Burg and Bouvard, who fhared the prize, have given new de- terminations of the moon's motion, fo well founded, that there is reafon to believe their tables will never vary more than fifteen or twenty feconds; viz. one half or a third less than Mason's, pub.

lifhed in England. Dr. Mafkelyne made him undertake them by determining the co-efficients of twenty-four equations of Meyer's tables by comparison with Bradley's.

The equations discovered by De La Flace, have brought them to greater perfection, and nothing now remains but the latitude. Burg has made a calculation of 3233 of Mafkelyne's obfervations, to certify the epoch of the moon. He alfo determined with more correctness Mafon's twenty-four equations of the moon. Madame Lavit calculated upwards of 500 places of the moon for Bouvard's refearches.

That able aftronomer Burckhardt, calculated lunar tables, according to Burg's refults, for the use of aftronomers fetting out on a distant expedition; as there may be fituations when it will be important for them to have exact calculations of the longitude.

The French Board of Longitude has offered a prize of 250l for more perfect lunar tables, which will fhortly be obtained. This branch, fo important to aftronomy and navigation, which has occupied full 100 years, is thus terminated in the most fatisfactory manner.

Dr. Parceval has concluded the grand analytical theory of the moon, giving precife formule for more equations than are mentioned in the before quoted tables. De La Place is likewife ocHe has finifhed a memoir of

cupied on the theory of the moon. the fatellites of Saturn and Herschel's planet. He proves that the fatellite of Saturn has an inclination, and afcertains the motion of its nodes.

Vidal has fent the rarest observations on Mercury, made at Mirepoix. This aftonishing obferver, who has done more in this respect than all the astronomers in the known world, has forwarded upwards of 500 obfervations on Mercury. He has been appointed Director of the National Obfervatory at Toulouse.

Burckhardt has difcovered a formula reprefenting the magnetic needle's declinations, observed at Paris fince 1580. It appears, its declination at Paris is 860 years; that the greatest declination weft is 30° 4' and takes place in 1878; the greatest eastern is only 23°.

The printing of tables of fines to thoufandth parts of the circle has been completed. Delambre put the last hand to them. Prony, at the Bureau du Cadastre, has also calculated more fully the decimal tables.

In the Ephemerides at Vienna, for 1800 and 1801, Triefnecker has made a collection of all the calculations of eclipfes obferved fince 1747, from thence to deduce the longitudes of the European and American cities, and the errors in the tables. Never was fo great a calculation of eclipfes; this able aftronomer has by this rendered government a most important service.

Goudin has by his Analyfis fully determined the eclipfe of 1847, the most considerable of the new century. Duvaucel, who has delineated eclipses for 30 years paft, has likewise delineated

D