of basalt, porphyry, green-stone; and veins of basalt having sides of pitch-stone traverse the sand-stone strata. These veins, it may be remarked, are of the same nature with those discovered in the island of Lamlash, and agree with those discovered in Iceland by Sir George Mackenzie.

III. Specific Gravity of Men.

In the year 1757, Mr. Robertson published in the Philosophical Transactions a set of experiments on the specific gravity of men. He constructed a vessel, in which men might be immersed, and he determined the specific gravity by the rise of the water in the vessel. Ten trials were made in this way on ten labouring men belonging to the ordinary of Portsmouth yard. They were all thin, and varied in size from 6 feet 2 inches to 5 feet 3 inches. I am induced to republish the results here, because I see it inserted in a contemporary Journal, that no experiments on this subject have ever been made. I have added a column exhibiting the specific gravity of the men, reckoning sea-water 1.000.

From this table we see that all the men were lighter than seawater, and that all, except one, were lighter than rain-water. The weight requisite to bring the lightest to the same specific gravity as rain-water would have been 28 lbs.; and to bring him to the specific gravity of sea-water very nearly 30 lbs would have been required; while the heaviest man was only 0.6 of a lb. lighter than sea-water.

SIR,

IV. Criopyrite.

(To Dr. Thomson.)

In consequence of some erroneous accounts which have made their way into the public papers, respecting a new engine of the power of twenty horses, said to be constructed under the direction of the inventor of the block machinery, it appears that the public, as well as your Dundee correspondent, are very anxious to gain some more faithful account of this wonderful machine, for which a

patent has been secured by Mr. Collier: a specification of which may be seen in the Repertory of Arts for November last.

That you may be impressed with a just idea of this new machine, now denominated a Criopyrite (or Fire Ram) I beg to send you an extract from a letter, which I received last week, from my friend Mr. Brunel (under whose directions I am carrying on the new works in this yard); in answer to a letter of mine about the criopyrite; speaking of which, he informs me, "that nothing is more preposterous than the account which has been published respecting this new engine; which it is stated, consumes no more than th part of the fuel required for a steam engine of the like power. It is true, that an attempt has been made with a view of obtaining all these advantages, which the Patentee anticipated as certain. Having been called upon to witness its action, and to give my aid in directing its power, I am able to assure you that the new engine, supposed to possess a power equal to twenty horses, has not yet, to my knowledge, moved without some external aid of two or three men. The account given out, is therefore a gross imposition; and as you have my sanction, I hope you will do all you can to correct it."

The machine at present being in embryo, your correspondent's wish for a diagram and description, I am sorry to say, cannot now be complied with.

If your correspondent will refer to any, or all of the following publications, he will find an account, and several tables relative to the elasticity and expansive force of steam, of different degrees of temperature. Gregory's Mechanics, vol. ii. pp. 55, 396, &c.: Brewster's Ferguson, vol. ii. p. 408: Buchanan on Fuel, p. 147, &c. : Mr. Dalton's table of the force of vapour, of each degree of Fahrenheit, in 5th vol. of Memoirs of Manchester Society; since republished in 6th vol. of Nicholson's Journal: Article Steam in Encyclopædia Britannica, &c. &c.

:

As to the incrustation on the inside of boilers, I imagine that the surest way of preventing it is by using none but water of the purest quality but unfortunately that cannot always be obtained. Having been told, that oyster-shells suspended in the boiler would prevent all incrustation, I lately tried the experiment. The result was, that upon examining the boiler at the end of a month, there was found no difference of incrustation, either upon the inside, the stone floats, or upon the shells.

Chatham, Dec. 12, 1815.

I remain, Sir, your obedient servant,

H. T. ELLICOMBE. V. Letter from Dr.Rees respecting Mr. Henry's Experiments on

SIP,

Bleaching.

(To Dr. Thomson.)

Dec. 1815.

Accustomed to the perusal of your publication, I observed in the 36th number, not without some degree of surprise, a letter addressed to me several years ago, and signed WILLIAM HENRY.

If the writer of that letter had condescended to direct his attention to the article OXYMURIATIC ACID, in the Cyclopædia, he would have found ample satisfaction on the subject of his correspondence. I shall content myself with referring him and the public to that article, without any further remark.

I remain, Sir, with great respect, your obedient Servant,

VI. New Method of preserving Meat.

A. REES.

M. Salmon Mauget, a French gentleman at present in London, has invented a new method of preserving meat. He makes the joint of meat undergo a certain process, which he conceals. This prevents putrefaction from taking place, after which the piece of meat may be hung up in the kitchen and gradually dried.

VII. Gunpowder.

A new mode of manufacturing gunpowder has been invented in France, we believe by M. Champy, who is at present in this country. The grains are spherical, of the size of swan-shot, well glazed, and composed of concentric coats. The advantages which it possesses over common gunpowder are that the manufacture of it is much cheaper, and that it burns at least six times more rapidly than common powder. A committee of the Institute was appointed by Louis XVIII. to examine this powder, before Bonaparte landed from Elba. They gave a favourable report concerning it. The mode of making this powder has not been made public.

VIII. Accidents from Scating.

Scarcely a winter passes over without one or more fatal accidents happening from scating in St. James's Park, when the sheet of water in the middle of it is covered with ice. When a person has the misfortune to fall into the water, by the breaking of the ice, it is hardly possible to give him any assistance. Whoever attempted it, would be almost sure to share his fate; so that in such cases, the unhappy young man is drowned, though surrounded by a crowd of friends and acquaintances, each anxious for his safety. It is rather surprising, that no precautions have been taken to prevent the fatal effects of falling through the ice in this place. If a small light boat were placed by the side of the water, it would be possible, by means of it, to save the life of the person who had fallen into the water. There is a still cheaper and simpler method which, I conceive, would be sufficient. If a rope were at hand, long enough to extend across the sheet of water, with a weight attached to it, it might be thrown to the person who had fallen through the ice; he would of course catch hold of it, and might be drawn out. Two or three such ropes should be placed at convenient distances along the lake, so as always to have one near at hand, at what place soever the scater falls in.

IX. Dew.

The phenomena of dew have been explained in so satisfactory a

manner by Dr. Wells, that the theory of this part of meteorology seems complete. Whether, however, this ingenious philosopher has not gone too far, when he affirms that dew is never deposited upon glass, unless it be colder than the atmosphere, the following fact, which I observed accidentally, leads me to doubt. A room, which I use as a laboratory, had been shut up for several months, in consequence of my illness, and during the whole of that time, no fire had been lighted in it. I entered it for the first time about the middle of November. The weather at that time was moist; but I could perceive no deposition of moisture upon any part of the walls, wooden furniture, or metallic apparatus in the room. But on removing a green cloth, with which my electrical machine was covered, I found the glass plate covered with a copious dew. Now I do not see how the temperature of this plate could have been lower than the wooden and metallic parts of the machine, on which, however, there was no dew. The whole machine had been covered with cloth, so that the radiation of heat was out of the question. I think it probable that when the air of a room becomes saturated with vapour, water will be deposited sooner upon glass than upon wood or metal, perhaps in consequence of a greater affinity between glass and water than between wood or metal, and that liquid. At least I do not see how the preceding fact can be explained upon any other supposition. Unfortunately I neglected to determine the temperature of the glass, the importance of the phenomenon not having occurred to me till afterwards. That of the room was about 43°.

X. Bibliothèque Britannique.

The present state of Europe has induced the Editors of this interesting work to extend their plan. Many common political interests will have a tendency to bring nations together, how different soever their language, manners, and religion may be. To the indifference, or rather the hatred, which has so long kept them at a distance from each other, will succeed a reciprocal curiosity, a desire to communicate the treasures of knowledge of every kind which have been accumulated by each nation, and to make every people participate in the discoveries of all the others. This commerce of exchanges, equally advantageous to all, will have a powerful tendency to maintain union among them. The antisocial prejudices will be gradually replaced by an enlightened sentiment respecting the advantage of a liberal system of communications; and benevolence will ultimately assume the place of hostility.

The editors of the Bibliothèque Britannique have directed their views towards this desirable result with perseverance, and not without some success, during a period of 20 years. At present they have conceived the idea of extending their plan without changing the spirit of the work, and of henceforth giving to their publication the name of Bibliothèque Universelle des Sciences, Belles Lettres,

et Arts. The work under this title will form a continuation of the Bibliothèque Britannique, though it will embrace a wider field.

This new Bibliothèque will contain every thing generally interesting in the literary and scientific journals of France, England, Germany, and Italy, and particularly extracts from original works on the sciences, the arts, and literature; and under the head biblio graphy, a notice of the principal works which shall appear in Europe. The work in consequence will become an universal medium of periodical eommunications.

The central situation of Switzerland is favourable to an undertaking of this nature; and Geneva, from its literary establishments, and the reputation of its philosophers, is fortunately placed to constitute the focus of such communications. Its political neutrality, at present so well secured, and that which the editors have always professed in the most difficult times, is a sufficient security of the impartiality which will always characterize the Bibliothèque Uni

verselle.

XI. Notice respecting Six's Thermometer.

The thermometer of Six is liable to an accident which, if not attended to, may very much impair the accuracy of its indications. A small portion of air is liberated from the alcohol it contains, which, getting into the tube, is found sometimes to increase, till it occupies as much as 5° in the scale, making the results so much too high. This happens annually, at the first approach of frosty weather. The remedy is to bring the instrument to the fire, and cause the bubble to pass to and fro in the warm spirit, getting it, if possible, into the large tube: by which means it is gradually absorbed, and does not soon reappear.

ARTICLE V.

Scientific Books in hand, or in the Press.

Mr. Bracy Clark, Veterinary Surgeon, of Giltspur-street, has in the Press, intended for speedy publication, a Treatise on the Bots of Horses, and other Domestic Animals, being a reprint of his treatise on that subject formerly published in the Linnean Society's Transactions, with numerous and interesting Additions. He has introduced an account of a newly discovered race of Flies bred in the living bodies of Animals in America.

Dr. Clanny, of Sunderland, will speedily publish a Treatise on the Mineral Waters of Gilsland, in which he will give the Medical Properties and Chemical Analysis of these Waters.

Dr. Henning, of the Hot Wells, Bristol, author of an Inquiry into the Pathology of Scrofula, is preparing for the press a work on Pulmonary Consumption, which will be ready for publication early in the spring.