the fleshy, in the last containing azot and more oxygen. By this means the change of muscles into a substance like spermaceti has been explained by Fourcroy; and it has been observed, that fat in the living body increases at the expense of the muscles, and vice

versa.

"The want of oxygen, considered as a cause of corpulency, is indicated by the analogy which exists between obesity and the sea scurvy, which seems only to be owing to a gradual abstraction of a part of the oxygen in the system. The sea-scurvy is never announced by meagreness, for a fulness of the habit is the first symptom of the disease. Dr. Trotter observes, that when a negro becomes rapidly corpulent, he never fails to be attacked by the scurvy, from which, according to the comparison of Dr. Beddoes, it appears that corpulency is to the scurvy what cachexy is to dropsy. According to Saussure and Humboldt, the atmosphere of high mountains contains less oxygen than that of lower regions, which explains why Condamine was attacked by scorbutic symptoms on the summit of Pinchina. All the symptoms of scurvy prove likewise that it arises from a privation of oxygen: thus the surface of the body is covered with livid spots, the arterial blood is very little fluid, and, after death, the left auricle is filled with venous blood, which Dr. Goodwin found in animals that had been deprived of life for want of oxygen.

Country people know from experience, that to fatten poultry, they must be kept in darkness; that substances proper for prolonging their sleep must be mixed with their food, as tares or spirituous liquors. It is a curious circumstance, that the age when the secretion of fat is most considerable is about the fortieth year, a time when the arterial system ceases to act such a conspicuous part in the animal economy: either, as Dr. Coindet thinks, it is then ossified, or in part obliterated, while the venous system coming more and more into action, acquires that influence so considerable in old age. Perhaps the arteries, the action of which is then visibly diminished, furnish the system with less oxygen at that period, which may be looked upon as the cause of the corpulency of middle-aged people.'

The plumpness of children, whose venous system is not yet developed,' is thus accounted for:

As respiration is more or less perfect, the blood may lose a greater or less quantity of carbon or hydrogen. In proportion as it loses less, the secretion of the fat will be more abundant, which affords an explanation of the enormous quantity of fat in amphibious animals, and fish, whose respiration is imperfect. They retain, therefore, more hydrogen and carbon, which passing into the arteries, Dr. Coindet thinks, occasion that considerable secretion of fat, found in fishes, in which the circulation is such, that almost the whole blood goes to the liver, either to operate there a secretion of fat, or of bile, the constituent parts of which do not differ much from those of the former. Diseases of the liver, such as scirrhous tumors, &c. are incident to people who are more or less corpulent.

The blood of plethoric, or fat people, is also commonly of a darkes colour, and more viscous than that of lean people, which last is generally very fluid. Those who drink cyder are more meagre than those accustomed to beer, porter, or other liquors of the same kind. In Holland, and in some parts of England, the inhabitants are very corpulent, whilst in France they are thin, from the above causes." Vol. II. P. 40-3:

We shall not be accused of the spirit of captiousness in thus regaling our readers with such a copious extract, which we have perhaps rendered somewhat more intelligible by abridging; but we confess, we have more than once been half inclined to suspect that our B. M. of Derby, at the name of which, the mineralogist will arch his brows, is better acquainted with some fashionable encyclopedists of the metropolis, than with the rural retreats of science, as his work may be considered a model of the modern conversazione style. Dr. A. informs: Dr. B. relates: Dr. C. thinks: Dr. D. imagines: Dr. E. supposes, &c. surely of all quackery, the quackery of philosophy is the most contemptible!!

Dr. Johnson, perhaps with as little authority as justice, denies Mr. Gibbs the merit of his method of separating animal oil from the different parts of animals, to bestow it gratuitously on Berthollet. Doubtless the chemist will be somewhat disappointed by a history of the lithic (uric) acid, in which the names of Wollaston, Pearson, or any other English philosopher do not appear! He has admitted, indeed, that Boyle discovered the phosphoric, and that Fisher described the formic acid in the Phil. Trans. 1670. This account is concluded with a confused process by Bonvoisin for separating, by means of sulphuric, the phosphoric acid from bones.

The account of poisons only furnishes the supposititious opinion that the venom of serpents is an animal gum.

'On the colouring matter.-Effects of Light.' It appears a generally received truth, that light is the agent, or efficient power, that deepens or renders more intense the colours in living bodies that the beasts and birds are brighter or deeper coloured in the equatorial than in the temperate climates: and that the human skin is black or tawny in the tropical and polar regions. Thus we can account for the coppery brown colour of the Laplanders and Samoides, as well as that of the Africans, not, as Buffon supposed, from the dryness of the air occasioned by the extremes of heat in the one and cold in the other; but from the action of light, of which it is evident the frigid zones enjoy a greater portion (principally reflected) than the temperate ones, otherwise perhaps animal life could not be supported in these regions. But if light gives intensity to the colour of living bodies, it still more certainly deprives them of those co

lours after death. In regard to its bleaching powers, the opinion that the rays of light effected a species of combustion, has been sufficiently exploded by the well-known affinity of light with oxygen; an affinity so powerful that it will revivify the oxydes of gold, silver, &c. change the oxymuriatic into common muriatic acid, and even deprive nitrous acid of more or less of its oxygen. Dr. Bancroft has shewn that it is yet to be ascertained, whether the colours which accompany or require the application of light, result directly from a combination of it with the coloured substances, or indirectly from its particular action in occasioning a separation of airs or their bases (and particularly of oxygen), or by favouring a combination thereof with the coloured matter. Thus, a solution of silver in the nitric acid becomes black in consequence of the loss of a certain portion of oxygen: the same is effected by the application of all inflammable bodies. Indigo receives its colour from the absorption of light and oxygen. We have repeatedly attempted to whiten linen with the oxymuriatic acid in a darkened room, but without success. It is therefore unreasonable to suppose that there is a combustion, (a term every person understands, but to which none have affixed a sufficiently explicit idea), or that light contributes to these effects on the colours of animal or other bodies, otherwise than by its affinity with oxygen, which affinity under some circumstances, and with the aid of perhaps other unknown affinities, sometimes separates and renders the oxygen elastic by uniting with it, and at other times occasions the combination of an increased portion of it, with the coloured substance. This is partly confirmed by the experiments of Davy and Beddoes, who whitened the fingers of a negro by means of muriatic phosoxyd (from s light, and dus acid) that appears capable of giving out a small portion of oxygen, and of still retaining all the light entering into its composition.

The following observations on phosphorescent light, and that of the glow-worm, are so immediately connected with this popular subject, that we cannot omit them.

Foster has observed, that the phosphoric part of the glow-worm (Lampyris splendidula, L.) is liquid, and if this animal be pressed between the fingers, the phosphorescence remains on them. According to Carradori, the phosphoric part of the Italian glow-worm (Lampyris Italica, L.) does not extend further than the last rings of the belly; it is there enclosed in an envelope or bag, composed of a membrane, one portion of which forms the superior, the other the inferior part of the belly, and which are united together. Behind this receptacle the phosphorus is found, resembling a paste, having the odour of garlic, and only a little savour: the phosphoric matter is squeezed out on the least pressure, but when separated from the body, it loses its splendour in a very short time, and is converted into a white dry matter.

• Carradori found, that the phosphorescent light of glow-worm (luccioloni [lucciolati] and lucciole) is suddenly extinguished if plunged into alcohol or vinegar, but continues to shine under oil, as well as in water or air: glow-worms, as well as the phosphorescent part detached from them, continue to shine under oil for hours together. If therefore these two kinds of glow-worms, which are of different species, and likewise phosphoric wood, continue to shine under oil, the light cannot proceed from a slow combustion, as Spallanzani prétends, since there is no air in oil to entertain it; and if the glow-worm shines under water, because, as Spallanzani maintains, the oxygen gas, which is one of the principles of the water, swells the combustion, why does not the phosphorus of Kunckel shine under water? Glow-worms continue to shine perfectly in vacuo. Carradori affirms, that the light of these insects is peculiar and innate; and as several other animals have the power of accumulating the electric fluid, and of keeping it condensed in peculiar organs, to emit and expand it afterward at will, so may the glowworms have the faculty of retaining, in a state of condensation, the fluid which constitutes light; that they may have the power even of extracting the light which enters into the composition of their aliments, and of transmitting it into the reservoir in their abdomen; or it is possible they may have the power of extracting the luminous fluid from the air, as other animals do heat from it by a chemical process; and the doctrine of Goettling on combined light, simpli fied by Brugnatelli, renders this opinion very probable,

That glow-worms emit a stronger and more lively light in oxygen gas, than in common air, does not depend on combustion, and its being rapidly excited, by the respiration of this gas, but arises from a more agreeable and lively existence they feel the same happens in other circumstances. Thus, when they fly freely without any interruption, their light is regular and beautiful; but once in our power, they either emit light irregularly or not at all. On being disturbed, they emit a frequent light, and this appears to be a mark of resentment; when placed upon their backs, they shine almost without interruption [intermission], by making continual ef forts to extricate themselves. During the day, they must be tormented to shine, a proof of its being the time of their repose.* They can shine at will in every point of their belly, a proof of their being able to move any part of it independent of the other, and they render this phosphorescence (or lucidity) more or less lively, and emit it as long as they please. On being plunged into warm and cold water, alternately, they shine with vivacity in the first, and extinguish their light in the last, another proof of an alternately agreeable and disagreeable sensation, giving rise to or diminishing it; in hot water, the light disappears by degrees. Hence their light does not depend on external causes, but on their will. From his experiments it appears that the phosphoric matter undergoes no soluble action except from water. The faculty of shining is not destroyed

Perhaps owing to its being the time rather of absorption than emission of light, and that this action form a part of their animal (conomy. Rev.

by incision or tearing open the belly: a small portion cut out will pass suddenly from the most beautiful brilliancy to a total extinction, and reassume in a moment its pristine brightness. This is attributed to a remnant of irritability, or more probably to the stimulus of the air, a mechanical irritation producing the same. A slight compression takes away their faculty of ceasing to shine. Exsiccation suspends the light, whilst softening in water makes it reappear again.'

Carradori thus proves, that the cause of phosphorescence is not from a slow combustion, as these insects shine in gases,improper for combustion; nor from the siccation of the azotic gas; but that it arises from a dissipation of aggregate light (light absorbed from the sun's rays). The Italian chemists, as well as Priestley and Wilson, have proved that light may combine and accumulate in bodies, in a greater or less quantity, according to their capacity for it: and it is unquestionably owing to this combination of light, and not to the omnificient powers of oxygen, as commonly supposed, that whiteness is communicated to vegetable stuffs by the modern process of bleaching. Doubtless the power and agency of light will be found infinitely more general and more applicable to the improvement of the arts, to horticulture, and even to medicine (in medicated waters, &c.) and agriculture, than philosophers have hitherto imagined.

The experiments of Dr. Hulme show that the lumination of herrings, mackarel, &c. is greatest in those which are fattest; that light begins to be emitted before any signs of putrefication appear, commonly on the second, and ending about the sixth day; and that the luminous property is destroyed as putrescence advances. That this light is a constituent principle of their bodies; that it may be separated from them by a peculiar process, (immersion in dilute aqueous solutions of Epsom and sea-salts, 2 drachms of the former to 2 ounces of water,) and retained and rendered permanent for some time, for it seems to be incorporated with their whole substance, and to form a part of them in the same manner as their other constituent principles. The soft roe abounds more with light than the flesh, while the hard roe is less luminous than the soft: the most luminous state of the latter was about the third or fourth night, when it appeared like a complete body of light. This spontaneous light is not accompanied with any sensible heat. As light is wholly incorporated with every part of their substance, it seems probable that it is the first constituent principle that escapes after the death of marine fishes. Heat,

B. Wil on on Light and Colours, &c. Rev.