other properties, peculiar to the various parts which compose the bodies of animals.

The whole of the blood, which by anatomists is divided into serum, red globules, and coagulating lymph, when chemically examined, is found to consist of albumen, gelatine, and fibre. The serum which remains liquid after the coagulation of the blood, is composed of albumen, gelatine, some saline matter, and much water. The clot, or crassamentum, also affords, by repeated washing, a large proportion of albumen and gelatine; after which a substance remains,, in appearance very analogous to muscular fibre, excepting that is in a more attenuated state. This substance, called fibrin by chemists, may be regarded as that part of the blood which has undergone the most complete animalisation; and from which the muscular fibre and other organs of the body are formed.

Experiments on the Ascent of the Sap in Trees. By Mr. KNIGHT.[1802.]

EARLY in the spring of 1799, he selected a number of young trees of different kinds, and made circular incisions round one-half of them, scraping off the external coat of the wood, the other half being left in their natural state. On the ascent of the sap they all shot with equal luxuriance, but that part of the stems which was below the incisions had scarcely any growth, while the parts above increased as rapidly as in the trees the bark of which had remained untouched.

From these experiments, varied in every way that occurred to him, Mr. Knight feels himself justified in concluding, that the current of sap, which adds to the annual layer of wood in the stem, descends through the bark, from the young branches and leaves.

Observations by Dr. HERSCHEL, with a view of investigating the Nature of the Sun, &c.-[1802.]

IT appears that this body has a planetary atmosphere, which extends to a great height, and is of great density: that, like ours, it is subject to agitations, and is transparent. This astronomer thinks that solar observations may hereafter be rendered as profitable to mankind as the Nilometer is to the Egyptians, and that, by certain indications, we may be able to predict the temperature of approaching seasons. He supposes it probable that there may be a certain connection between the price of corn, or rather the abundance and scan

tiness of harvest, and the number of spots on the sun's surface.

In proof of this he has given a statement of the prices of wheat, and the spots on the sun's disk, during five remarkable periods between 1650 and 1713. He considers the sun's spots to be symptoms of a copious emission of light and heat; and that in proportion as their number is greater or less, may be expected more or less abundant crops of corn.

In a second paper on the same subject, Dr. Herschel proposes thermometrical observations, as a future criterion of a defective or copious emission of the solar rays. He suspects that one half of the sun is less favourable to a copious emission of rays than the other; and that its variable lustre may possibly appear, to other solar systems, as irregular periodical stars are seen by us.

Experiments on the Light which is spontaneously emitted from various Bodies, and on Solar Light. By Dr. HULME.

Ir appears, from the first series, that objects, as fish, which abound with spontaneous light in a latent state, do not emit it, when deprived of life, but from such parts as have been some time in contact with the air, and that a blast from bellows does not increase this species of light, as it does that which proceeds from combustion.

From a second series it appears, that oxygen gas does not act upon this light, so as to render it more vivid than it is in atmospherical air.

From the third series, it is deserving of remark, that azotic gas is favourable to the spontaneous light emitted from fishes, but extinguishes that proceeding from rotten wood.

From the fourth and fifth it appears, that hydrogen and carbonic acid gases prevent the emission of spontaneous light, and extinguish it when emitted.

The next three series of experiments show, that sulphurated hydrogen gas extinguishes spontaneous light sooner than carbonic acid gas; that nitrous gas prevents the emission of light, and extinguishes that which is emitted, and that it is completely extinguished in a vacuum.

From some other experiments it appears, that solar light, when imbibed by Canton's phosphorus, is subject to the same laws, with respect to heat and cold, as the spontaneous light of fishes, rotten wood, and glow-worms.

On the Theory of Light and Colours. By Dr. YOUNG. THE three essential hypotheses noticed by Dr. Young, and considered by him literally as parts of the more complicated Newtonian system, are,

1. That a luminiferous ether pervades the universe, rare and elastic in a high degree.

2. That undulations are excited in this ether whenever a body becomes luminous; and,

3. That the sensation of different colours depends on the different frequency of vibrations excited by light in the retina.

The fourth hypothesis, viz. That all material bodies have an attraction for the ethereal medium, by means of which it is accumulated within their substance, and for a small distance around them, in a state of greater density, but not of greater elasticity, is diametrically opposite to that of Newton, but considered by Dr. Young as the most simple and best capable of explaining the phenomena.

Experiments and Observations on certain Stony Substances, which at different Times are said to have fallen on the Earth. By LUKE HOWARD, Esq.-[1802.]

WE have here historical accounts of all those facts on the subject which seem to be well authenticated. Particular mention is made of one that fell in Portugal in 1796; of about a dozen that fell at Sienna in July, 1794; of one that weighed 56 lbs. that fell in December, 1795, near Wold-cottage, in Yorkshire: and of others that fell in 1798, near Benares, in the East Indies.

We have then a mineralogical description of these various stones, by the Count de Bournon; after which, Mr. Howard proceeds to consider the assistance to be derived from the science of chemistry, in distinguishing them from all other known substances, and in establishing the assertion that they have fallen on the earth.

Count de Bournon's description of native iron, and Mr. Howard's examination of specimens of iron from South America, Bohemia, and Senegal, follow in succession; from which the author, instead of drawing any conclusions, proposes the following queries:

1. Have not all fallen stones, and what are called native irons, the same origin?

2. Are all or any, the produce, or the bodies of meteors?

3. Might not the stone from Yorkshire have formed a meteor in regions too elevated to be discovered?

On the Construction of the Heavens. By Dr. HERSCHEL. Dr. H. has taken a very enlarged view of the sidereal bodies of the universe; and has enumerated a great diversity of parts that enter into the construction of the heavens. The first species are insulated stars, such as the author considers our sun, and all the brightest stars, which he supposes are nearly out of the reach of mutual gravitations; for, stating the annual parallax of Sirius at 1", he calculates that Sirius and the sun, if left alone, would be 33,000,000 of years in falling together, and that the action of the stars in the milky way, as well as others, would tend to protract this time much

more.

He conjectures that insulated stars alone are surrounded with planets. With respect to double stars, he thinks that they preserve their relative distances by a periodical revolution round a common centre. The same theory he applies to triple, quadruple, and multiple systems of stars; and pursues his conjectures still farther to clusters and groups of stars, as well as to the nebulæ, some of which he thinks may be so distant, as for the rays of light to take 2,000,000 of years in travelling from them to our system.

Account of some cases of the production of Colours not hitherto described. By Dr. YOUNG.-[1803.]

His method of accounting for atmospherical haloes is as follows: When a number of fibres of the same kind, for instance a uniform lock of wool, is held near the eye, we see an appearance of haloes surrounding a distant candle; but their brilliancy, and even their existence, depends on the uniformity of the dimensions of the fibres, and they are larger as the fibres are smaller. It is obvious that they are the immediate consequences of the coincidence of a number of fringes of the same size; which, as the fibres are arranged in all imaginable directions, must necessarily surround the luminous object at equal distances on all sides, and constitute circular fringes.

There can be little doubt that the coloured atmospherical haloes are of the same kind; their appearance must depend on the existence of a number of particles of water, of equal dimensions, and in a proper position with respect to the luminary and the eye. As there is no natural limit to the magnitude

of the spherules of water, we may expect these haloes to vary without limit in their diameters; and it has been observed not only that their dimensions are various, but that they frequently change during the time of observation.

A Catalogue of 500 new Nebula, Nebulous Stars, Planetary Nebula, and Clusters of Stars, with Remarks on the Construction of the Heavens. By Dr. HERSCHEL. — [1803.]

IN dividing the different parts of which the sidereal heavens are composed in proper classes, Dr. Herschel is obliged to examine the nature of the various celestial objects that have been hitherto discovered, in order to arrange them in a manner most conformable to their construction. He first treats of insulated stars. It might be expected that the solar system would stand foremost in the list, whereas, by treating of insulated stars, we seem, as it were, to overlook one of the great component parts of the universe. It will, however, appear that this very system, magnificent as it is, can only rank as a single individual belonging to the species which we are going to consider.

By calling a star insulated, Dr. Herschel does not mean to denote its being totally unconnected with all other stars or systems; but when stars are situated at such immense disstances from each other as our Sun, Arcturus, Capella, Lyra, Sirius, and numberless others, we think that we may look upon them as sufficiently out of the reach of mutual attrac tions, to deserve the name of insulated stars. For it is as+ certained by computation that, supposing the earth's orbit, as is highly probable, does not subtend more than an angle of one second of a degree, when seen from Sirius, then the Sun and Sirius, if the masses are equal, would not fall together in less than thirty-three millions of years, even though they were not impeded by many contrary attractions of other neighbouring insulated stars. A star thus situated may cer→ tainly deserve to be called insulated, and of this kind our Sun is probably one.

From the detached situation of insulated stars, it appears that they are capable of being centres of extensive planetary systems; and from analogy we may suppose, that every one of them is attended with planets, satellites, and numerous comets; though there is good reason for believing that we can only look for solar systems among insulated stars.

The next part of the construction of the heavens, is the union of two stars, that are formed together into one system,