reduced a portion of isinglass to the state of coal, and digested it in nitric acid, which at first did not appear to act upon it, but at length slowly dissolved almost the whole of it. The solution resembled those which have been described, but was of a deeper brown colour; and, when evaporated to dryness, left a residuum, which, upon being examined by the re-agents employed in the former experiments, was found to produce similar effects.

It appears evident, therefore, that tan may be formed from animal as well as from vegetable and mineral coal; and it also appears, from what has been stated, that it is composed of carbon, combined with a certain proportion of oxygen. It seems, however, necessary that In

the carbon should be uncombined with any other substance. support of this opinion, Mr. Hatchett mentions the following experiments :

1. A piece of Bovey coal, which appeared like half-charred wood, upon being treated with nitric acid, formed a solution of a deep yellow colour: this solution, when evaporated, left a residuum, which, dissolved in distilled water, and examined by various re-agents, particularly by gelatine, did not show any signs of its containing tan ; the predominant substance appearing to be oxalic acid.

2. Another piece of Bovey coal, which was more perfectly carbonized, afforded a brown solution, which, unlike the former, yielded a considerable quantity of tan.

3. A portion of the first-mentioned sort of Bovey coal, by being exposed to a red heat in a close vessel, and then treated as before, was thus converted, almost entirely, into tan.

4. A coal from Sussex, very like the second sort of Bovey coal, also afforded tan.

5. A piece of Surturbrand, from Iceland, yielded a similar result. 6. Deal sawdust, treated in the same manner as the former substances, afforded oxalic acid, but not any tan.

7. Another portion of the same sawdust was reduced into charcoal, which, treated as before, was thereby converted into tan.

8. Teak wood, which Mr. Hatchett had previously ascertained not to contain either gallic acid or tan, was reduced into charcoal, which was as readily converted into tan as the substances already mentioned.

Mr. Hatchett then adverts to a series of experiments he is making on the slow carbonization of vegetable substances in the humid way, a few of which, he says, he is compelled to notice, on account of their being intimately connected with the present subject. In these experiments he has observed, that concentrated sulphuric acid dissolves resinous substances, forming a yellowish brown transparent solution, which, by digestion, becomes intensely black. Concentrated sulphuric acid readily dissolves the common turpentine of the shops. If a portion of this solution be immediately poured into cold water, the turpentine is precipitated, in the state of common yellow resin. But if another portion of the same solution be, after the lapse of an hour or more, poured into cold water, the resin thus formed is not yellow,

but dark brown.

If four or five hours elapse before the solution is poured into the water, the resin precipitated is found to be completely black. And if the digestion is continued for several days, or until there is no longer any production of sulphureous gas, the turpentine is converted into a black porous coal, which does not contain any resin, although a substance hereafter noticed may frequently be separated from it by digestion in alcohol.

When common resin was treated in the same manner, about 43 per cent. of the coal was obtained, which, after exposure to a red heat in a loosely-covered platina crucible, still amounted to more than 30 per cent., and appeared to possess properties very similar to those of some of the mineral coals.

Mr. Hatchett having obtained, in the manner above described, yellow resin, brown resin, black resin, and coal, from a quantity of common turpentine, dissolved a portion of each of these, and also of the turpentine, in nitric acid, and then reduced the solutions to dryThe residua, which varied in colour, from yellow to dark brown, were dissolved in distilled water, and examined by solution of isinglass and other re-agents.

ness.

1. The solution of the residuum of turpentine was of a pale straw colour, and did not contain any tan.

2. That of the yellow resin resembled the former in every respect. 3. That of the brown resin was of a deeper yellow, but did not afford a vestige of tan.

4. That of the black resin, on the contrary, afforded a considerable portion of tan.

5. That of the coal afforded tan in great abundance.

Hence it appears, that these modifications of turpentine yield tan only in proportion to the quantity of their original carbon, progressively converted into coal.

Other substances, particularly various kinds of wood, copal, amber, and wax, when reduced into coal in the humid way, were in like manner converted into tan by nitric acid.

But tan may, Mr. Hatchett says, be artificially produced, without the help of nitric acid; for if any of the resins, or gum resins, after long digestion with sulphuric acid, are digested with alcohol, a dark brown solution is formed, which, by evaporation, yields a mass that is soluble in water or in alcohol, and which copiously precipitates gelatine, acetate of lead, and muriate of tin, but produces only a slight effect on oxymuriate of iron.

In the subsequent section of this paper, Mr. Hatchett mentions some circumstances which induce him to think that a natural process, similar to those above described, sometimes takes place in peat moors, and that tan has been, and continues to be, formed during the gradual carbonization and conversion of the vegetable matter into peat. Supposing this opinion to be correct, it seems, he says, at first difficult to conceive how the formation of tan is effected during the growth of those vegetables from which it has hitherto been obtained; but after adverting to the experiments and observa

tions of Mr. Biggin and Mr. Davy, which show that the proportion of tan in the same trees is different at different seasons, and that it is principally contained in the white interior bark, which bark is comparatively most abundant in young trees, he observes, that there seems to be an intimate connexion between the formation of new wood and the formation of tan, in those vegetables which afford the latter; and thinks it very probable that such vegetables have the faculty of absorbing more carbon and oxygen than is required in the formation of the vegetable principles, especially of the woody fibre; and that this excess of carbon and oxygen, by chemical combination, becomes tan, which is secreted in the white interior bark, and afterwards decomposed, and employed in the formation of the new wood.

The ligneous substance of vegetables, Mr. Hatchett says, appears to be composed of carbon, oxygen, hydrogen, and nitrogen; and he has reason to think, from some synthetical experiments he has made, that tan consists of 53 parts of pure carbon, and 47 of oxygen.

In the concluding section, Mr. Hatchett observes, that the whole of the present paper may be concentrated into one simple fact, namely, that tan is composed (at least essentially) of carbon and oxygen; and that, although it has hitherto been deemed a peculiar principle, formed by nature in certain vegetables, it may, with the greatest ease, be produced, by presenting oxygen to carbon in the humid way, under the circumstances which have been described.

Since the experiments which have been related were made, Mr. Hatchett has, he says, further proved the efficacy of the factitious tan by actual practice; as he has converted skins into leather by means of tan produced from materials which, to professional men, must appear extraordinary, such as deal sawdust, asphaltum, turpentine, pit-coal, wax candle, and a piece of the same sort of skin. Allowing, therefore, that the artificial production of tan must for the present be principally regarded only as a curious chemical fact, not altogether unimportant, yet, as the principle on which it is founded has been developed, we may, Mr. Hatchett thinks, hope that a more economical process will be discovered, so that every tanner may be enabled to prepare his tan, even from the refuse of his present materials.

The Case of a full-grown Woman in whom the Ovaria were deficient. By Mr. Charles Pears, F.L.S. Communicated by the Right Hon. Sir Joseph Banks, K.B. P.R.S. Read May 9, 1805. [Phil. Trans. 1805, p. 225.]

The woman whose case is here described was born in Radnorshire in the year 1770. She was of a fair complexion, and, except when irritated, of a mild temper. In her diet she was remarkably abstemious, eating very little, either of animal or vegetable food; and if at any time she ate a hearty meal, or took several kinds of food, she was so much affected by it as to faint. She was of a costive habit,

seldom having a passage oftener than once in nine days, sometimes only once in fourteen days. She ceased to grow at ten years of age, and was only four feet six inches in height. Across the shoulders she measured fourteen inches, but her pelvis measured only nine inches, from the ossa ilia to the sacrum. Her breasts and nipples never enlarged more than those of a man; nor did she ever menstruate, or show any other sign of puberty, either in mind or body; on the contrary, she always expressed aversion to the familiarities of young men.

At the age of twenty-one she became uneasy at finding herself different from other women, and, attributing the difference to her not having menstruated, frequently applied for medical advice.

She was, from her infancy, subject to the attacks of a complaint in the chest, attended with cough. These attacks increased in violence as she advanced in age; and in her twenty-ninth year, one of them came on, attended with convulsions, of which, after a few hours, she died.

Upon examining the female organs after her death, it appeared that the os tincæ and uterus had the usual form, but had not increased beyond their size in the infant state. The passage into the uterus, through the cervix, was oblique, and the Fallopian tubes were pervious to the fimbria. The ovaria were so indistinct that they rather showed the rudiments which ought to have formed them, than any part of their natural structure.

From the history of the preceding case, it appears, not only that an imperfect state of the ovaria is attended with an absence of all the characters belonging to the female after puberty, but also that the uterus itself, although perfectly formed, was checked in its growth, in consequence of the imperfect structure of those parts.

A Description of Malformation in the Heart of an Infant. By Mr. Hugh Chudleigh Standert. Communicated by Anthony Carlisle, Esq. F.R.S. Read May 9, 1805. [Phil. Trans. 1805, p. 228.] The infant here treated of died at the age of ten days, during which period nothing particular was remarked, except that the skin exhibited the blue colour so common in cases of imperfect pulmonary circulation.

Upon opening the body, all the viscera were found in the natural state, except the heart, which exhibited the following remarkable structure:

Externally, only one auricle could be perceived, into which the pulmonary veins and venæ cave entered in the usual manner. The pulmonary artery was wanting, and the body of the heart had but one ventricle, which was separated from the auricle by tendinous valves, and opened into the aorta.

The auricle was also single, and had a narrow muscular band, which crossed the ostium venosum, in the place of the septum. The aorta sent off an artery from the situation of the ductus arteriosus: this

artery was divided into two branches, to supply the lungs. These vessels were of small diameter.

The pulmonary veins were four in number; but the area of these, and that of the vessel which acted as the pulmonary artery, did not exceed half the usual dimensions.

The child, while alive, was seen by Dr. Combe, who did not observe that its respiration, temperature, or muscular action, were materially affected.

On a Method of analysing Stones containing fixed Alkali, by Means of the Boracic Acid. By Humphry Davy, Esq. F.R.S. Professor of Chemistry in the Royal Institution. Read May 16, 1805. [Phil. Trans. 1805, p. 231.]

The method of analysis here described by Mr. Davy is founded on the attraction of the boracic acid for the simple earths, which is considerable at the heat of ignition, and on the ease with which the compounds formed with them are decomposed by the mineral acids.

The process is as follows: 100 grains of the stone to be examined must be fused for about half an hour, in a strong red heat, with 200 grains of boracic acid: an ounce and a half of nitric acid, diluted with seven or eight times as much water, must be digested upon the mass till the whole is decomposed; and the fluid must then be reduced, by evaporation, to an ounce and a half or two ounces.

If the stone contain silex, it will now be separated: this must be collected upon a filter, and washed with distilled water till freed from the boracic acid and all other saline matter.

The water that has passed must be mixed with the other fluid, and the mixture evaporated till it is reduced to a convenient quantity, for instance, half a pint. It must then be saturated with carbonate of ammonia, and boiled with an excess of this salt till all precipitable matter has fallen to the bottom of the vessel.

The earths and metallic oxides must be separated by the filter, and to the filtered liquor must be added nitric acid, till it tastes very sour: it must then be evaporated till the boracic acid appears free.

The fluid must be again passed through the filter, and evaporated to dryness; when, by exposure to a degree of heat equal to 450° of Fahrenheit, the nitrate of ammonia will be decomposed, and the nitrate of fixed alkali will remain in the vessel.

The remaining earths and oxides Mr. Davy has separated by the usual processes. The alumina he has separated by solution of potash; the lime by sulphuric acid; the oxide of iron by succinate of ammonia; the manganese by hydrosulphuret of potash; and the magnesia by pure soda.