low, and consequently produces a greater quantity of light and heat.

Lac is a substance very similar to wax in the manner of its formation; it is the product of an insect which collects its ingredients from flowers, apparently for the purpose of protecting its eggs from injury. It is formed into cells fabricated with as much skill as those of the honey-comb, but differently arranged. The principal use of lac is in the manufacture of sealing-wax, and in dying scarlet.

Musk, civet, and castor, are other particular productions, from different species of quadrupeds. The two first are very powerful perfumes; the latter has a nauscous smell and taste, and is only used medicinally.

Caroline. Is it from this substance that castor oil is obtained?

Mrs. B. No. Far from it, for castor oil is a vegetable oil, expressed from the seeds of a particular plant; and has not the least resemblance to the medicinal substance obtained from the castor.

Silk is a peculiar secretion of the silk worm, with which it builds its nest or cocoon. This insect was originally brought to Europe from China. Silk, in its chemical nature, is very similar to the hair and woal of animals. The moth of the silk worm ejects a liquor which appears to contain a particular acid, called bombic, the properties of which are very little known.

Emily. Before we conclude the subject of the animal economy, shall we not learn by what steps animals return to their elementary state?

Mrs. B. Animal matter, although the most complicated of all natural substances, returns to its elementary state by one single spontaneous process, the putrid fermentation. By this, the gelatine, albumen, and fi brine, are slowly reduced to the state of oxygen, hydrogen, nitrogen, and carbone; and thus the circle of changes through which these principles have passed is finally completed. They first quitted their elementary form, or their combination with unorganized matter, to enter into the vegetable system.-Hence they were transmitted to the animal kingdom; and from

this they return again to their primitive simplicity, soon to re-enter the sphere of organized existence.

When all the circumstances necessary to produce fermentation do not take place, animal, like vegetable matter, is liable to a partial or imperfect decomposition, which converts it into a combustible substance very like spermaceti. I dare say that Caroline, who is so fond of analogies, will consider this as a kind of animal bitumen.

Caroline. And why should I not, since the processes, that produce these substances are so similar.

Mrs. B. There is, however, one considerable difference; the state of bitumen seems permanent, whilst that of animal substances, thus imperfectly decomposed, is only transient; and, unless precautions be taken to preserve them in that state, a total dissolution infallibly ensues. This circumstance, of the occasional conversion of animal matter into a kind of spermaceti, is of late discovery. A manufacture has in consequence been established near Bristol, in which, by exposing the carcases of horses and other animals for a length of time under water, the muscular parts are converted into this spermaceti-like substance. The bones afterwards undergo a different process to produce hartshorn, or, more properly, ammonia, and phosphorous; and the skin is prepared for leather.

Thus art contrives to enlarge the sphere of useful purposes, to which the elements were intended by nature; and the productions of the several kingdoms are frequently arrested in their course, and variously modified, by human skill, which compels them to contribute, under new forms, to the necessities or luxuries of man.

But all that we enjoy, whether produced by the spontaneous operations of nature, or the ingenious efforts of art, proceed alike from the goodness of Providence.-To GOD alone man owes the admirable faculties which enable him to improve and modify the productions of nature, no less than those productions themselves. In contemplating the works of the creation, or studying the inventions of art, let us, therefore, never forget the Divine Source from which they proceed; and thus every acquisition of knowledge will prove a lesson of piety and virtue

E e

END OF THE LONDON COPY

An abridgement of the Bakerian Lecture on the decomposition of the fixed alkalies and the exhibition of the new substances which constitute their bases: by Humphrey Davy, esq. secretary of the Royal Society.

THE researches I had made on the decomposition of acids, and of alkaline and earthly neutral compounds, proved that the powers of electrical decomposition were proportional to the strength of the opposite electricities in the circuit, and to the conducting power and degree of concentration of the materials employed. In the first attempts I made on the decomposition of the fixed alkalies, I acted upon aqueous solutions of potash and soda, saturated at common temperatures, by the highest electrical power I could command, and which was produced by a combination of voltaic batteries, belonging to the Royal Institution, containing 24 plates of copper and zinc of 12 inches square, 100 plates of 6 inches, and 150 of 4 inches square, charged with solutions of alum and nitrous acid; but in these cases, though there was a high intensity of action, the water of the solutions alone was effected, and hydrogen and oxygen disengaged with the production of much heat and violent effervescence. The presence of water appearing thus to prevent any decomposition, I used potash in igneous fusion. By means of a stream of oxygen gas from a gasometer applied to the flame of a spirit lamp, which was thrown on a platina spoon containing potash, this alkali was kept for some minutes in a strong red heat, and in a state of perfect fluidity. The spoon was preserved in communication with the positive side of the battery, of the power of 100 of inches, highly charged; and the connection from the neg ative side was made by a platina wire. By this ar rangement some brilliant phenomena were produced. The potash appeared a conductor, in a high degree, and as long as the communication was preserved, a most intense light was exhibited at the negative wire, and a column of flame, which seemed to be owing to the devel opement of combustible matter, arose from the point of contact. When the order was changed, so that the platina spoon was made negative, a vivid, constant light

appeared at the opposite point. There was no effect of inflammation round it, but æriform globules, which inflamed in the atmosphere, rose through the potash. The platina, as might have been expected, was considerably acted upon; and in the cases when it had been negative in the highest degree.

The alkali was apparently dry in this experiment; and it seemed probable, that the inflammable matter arose from its decomposition. The residual potash was unaltered; it contained, indeed, a number of dark grey metallic particles, but these proved to be derived from the platina.

I tried several experiments on the electrization of potash, rendered fluid by heat, with the hopes of being able to collect the combustible matter, but without success; and I only attained my object, by employing electricity, as the common agent for fusion and decomposition. Though potash, perfectly dried by ignition, is a non-conductor, yet it is rendered a conductor by a very slight addition of moisture, which does not per ceptibly destroy its aggregation; and in this state it readily fuses and decomposes by strong electrical pow.

ers.

A small piece of pure potash, which had qeen exposed for a few seconds to the atmosphere, so as to give conducting power to the surface, was placed upon an insulated disc of platina, connected with the negative side of the battery, of the power of two hundred and fifty of six and four, in a state of intense activity; and a platina wire, communicating with the positive side, was brought in contact with the upper surface of the alkali. The whole apparatus was in the open atmosphere.

Under these circumstances, a vivid action was soon observed to take place. The potash began to fuse at both its points of electrization. There was a violent effervescence at the upper surface at the lower or negative surface, there was no liberation of elastic fluid; but small globules, having a high metallic lustre, and being precisely similar, in visible characters to quicksilver, appeared; some of which burnt with explosion, and bright flame, as soon as they were formed, others remained, and were merely tarnished, and

finally covered by a white film, which formed on their surfaces. These globules, numerous experiments soon showed to be the substance I was in search of, and a peculiar inflammable principle the basis of potash. I found that the platina was in no way connected with the result, except as the medium for exhibiting the elec trical powers of decomposition; and a substance of the same kind was produced, when pieces of copper, silver, gold, plumbago, and even charcoal were employed for completing the circuit. The phenomenon was independent of the presence of air. I found that it took place when the alkali was in the vacuum of an exhausted receiver. The substance was likewise produced from potash fused by means of a lamp, in glass tubes confined by mercury, and furnished with hermetically inserted platina wires, by which the electrical action was transmitted. But this operation could not be carried on for any considerable time; the glass was rapidly dissolved by the action of the alkali, and this substance soon penetrated through the body of the tube.

Soda, when acted upon in the same manner as potash, exhibited an analogous result; but the decomposition demanded greater intensity of action in the batteries, or the alkali was required to be in much thinner and smaller pieces. With the battery of one hundred of six inches in full activity, I obtained good results from pieces of potash weighing from forty to seventy grains, and of a thickness which made the distance of the electrified metallic surfaces nearly a quarter of an inch; but with a similar power it was impossible to produce the effects of decomposition on pieces of soda of more than fifteen and twenty grains in weight, and that only when the distance between the wires was about one eighth or one tenth of an inch.

The substance produced from potash remained fluid at the temperature of the atmosphere at the time of its production; that from soda, which was fluid in the degree of heat of the alkali during its formation, be came solid on cooling, and appeared having the lustre of silver.

When the power of two hundred and fifty was used with a very high charge for the decomposition of soda,