acid were given out. The iron was evidently in the state of protoxide, for crystals of protosulphate of iron were obtained. Indeed, no percarbonate of iron probably exists, or, at any rate, none has been described, and it cannot be formed artificially.

c. 200 grains of the ore were treated with muriatic acid; nitric acid was added to convert the protoxide of iron into peroxide. The solution was decomposed by ammonia, and the peroxide of iron precipitated, being washed, dried, and ignited, weighed 97.5 grains. On repeating the experiment, the mean result was 96.15 48-075 per cent. The iron in the ore exists as already mentioned in the state of protoxide; and as 40 peroxide are equivalent to 36 protoxide, 48-075 are equal to 43.26 protoxide of iron, which is the quantity contained in 100 grains of the ore.

d. The residuum insoluble in muriatic acid was of a dark colour, and after being moderately dried, it was heated to redness in a platina crucible; by this it became perfectly white, and lost 5.33 grains, which is the weight of the carbonaceous matter. The insoluble residuum, consisting of silica and alumina, gave a mean of 18 12 per cent.

e. The ammoniacal solution, after the separation of the iron, was treated with carbonate of ammonia; by this a quantity of carbonate oflime was thrown down; it weighed in one experiment 7, and in the other 6.5 grains, giving a mean of 374 of lime, which of course existed in the ore in the state of car bonate.

f. The ammoniacal solution, evaporated so as to expel all excess of ammonia, was treated with prussiate of potash; a precipitate of a light pinkish hue was obtained, but the quantity was too small to allow of determining the quantity of oxide of manganese which it indicated.

It will then appear that the ore, usually, but improperly, called argillaceous iron ore, is, in fact, a carbonate of iron, consisting of ›

As an atom of carbonic acid is represented by 22, and one of protoxide of iron by 36, the 43.26 of protoxide which the ore contains must be combined with nearly 26.4 of the 29.3 of carbonic acid, leaving 29 to combine with 3.74 of lime, a quantity of carbonic acid which exceeds but little the requisite proportion, and which will not account for the excess in the analysis. Although in this ore from Yorkshire the quantity of oxide of manganese is extremely small, there are some of the ores in Wales which contain nearly 10 per cent of it.

DICTIONARY OF CHEMISTRY.

ALKANET. A plant cultivated in the southern parts of Europe; the root of which is the principal colouring matter of oils, wax, and lip-salve.

ALLOY. In common life, the mixture of a baser with a more valua ble metal; in chemistry, all compounds of two or more metals are called alloys, except when mercury is one of the metals, the compounds with mercury being called amalgams. Very useful tables of the properties of various alloys are published in most treatises on chemistry.

ALLUVIAL FORMATIONS, in geology, that soil which is deposited by water, and which is generally the result of the destruction of some hills or mountains.

ALMONDS. A fruit, of which there are two sorts; one of which, bitter almonds, is poisonous to birds, animals, and, if taken in sufficient quantity, to men. A great quantity of oil is obtained from this fruit by simple pressure.

ALOE. The name of a plant, the leaves of which yield a bitter juice, well known, in its dried state, as a medicine. There are three kinds

of the medicine aloes, all of which are made in Spain.

ALUDEL. The name, among the elder chemists, of a particular species of receiver for the products of sublimation, which is now no longer in use.

ALUM. Sulphate of alumina. ALUM-EARTH. A particular species of mineral, of a blackish brown, dull, and somewhat slaty.

ALUM-SLATE. Also a mineral, of which there are two kinds, the common and glossy.

ALUMINA. A white powder obtained from alum, and various other substances; and which was considered to be an elementary earth, till Sir Humphrey Davy's discoveries led to the supposition of its being a metallic oxide. Under the idea of its being an element, the authors of the present nomenclature of chemistry, proceeding on the proper principle, that the chemical names of all substances should, as far as possible, express their chemical nature, have given to the combination of this earth

with acids, the name of salts of alumina; and each individual salt is again distinguished by the addi

tion of the name of the acid with which it is formed. Thus the sul phate of alumina is a compound of sulphuric acid and alum. Throughout this Dictionary, therefore, we shall place, under the respective bases of different salts, all those, and only those, which are at the same time known by some other name. Thus,

ALUMINA, sulphate of. Alum. ALUMINITE. An ore of alum, found in the neighbourbood of Halle in Saxony.

ALUMINUM. The supposed metallic base of alumina.

AMADOU. German tinder; a substance much in use on the Continent for lighting pipes, &c.

AMALGAM. The combination of mercury with another metal.

AMBER. Supposed to be an indurated vegetable production, it yielding, on analysis, the same constituents as vegetable substances. It is of various uses in the arts.

AMBERGRIS. A substance found

on the coasts, principally of tropical climates, and in the intestines of the spermaceti whale. It is a light, soft substance, which swims on the water, and is much used by the perfumer.

TO PREVENT BURNING THE

FINGERS.

Boys who delight in snap-dragon, as we were wont to do, may like to know the following useful receipt when playing such games. We cannot, at the same time, recommend any body to try their fingers in any other burning matter except a plate of brandy. Pound cherry-tree gum and alum, in equal quantities, into powder, and mix the powder with strong wine vinegar, and leave it in a vessel over hot ashes to digest for 24 hours. Any thing rubbed with this composition, after it has become cold, will not burn.

A. M. will observe that his proposition TO CORRESPONDENTS. several more letters have reached us has been very favourably received; and from Gentlemen who wish to join the Society. We think, therefore, that it state what he means further to do; and will shortly be necessary for him to we should like to hear from him on the subject. A.P., G.R., Experimentum, received. We shall hand over the latW. H. S., and W.A. S. have all been ter's note to A. M., and we shall comthe same Correspondent, as they seem municate the suggestions of A. P. to

to us

us more matters for private discussion and arrangement than for public remark.

Unfortunately the second communication of A Young Philosopher came too late to enable us to comply with his request. We trust, however, that whatever objections he might have had to our doing what we have done, will be removed by what we have said, kila

Communications (post paid)to be addressed to the Editor, at the Publishers'.

London: Published by JOHN KNIGHT

and HENRY LACEY, 24, PaternosterPrinted by B. Bensley, Boltcourt, Fleet-street.

row

and depth. The improved construction, which we are about to explain, affords a means of reducing the depth of the tank, dispensing with the bridge of suspension, and of increasing at pleasure the capacity of the gasometer upon a given base; thus rendering a small apparatus capable, if required, of holding a large quantity of gas, the first cost of which will be considerably less than even a small gasometer constructed upon the ordinary plan.

Mr. Tait, of Mile-end-road, the inventor, has, we believe, been for some years connected with gas establishments, and is therefore fully aware of the practical defects or advantages of the different constructions of gasometers now in use. The plate is a section of his improved contrivance :—a a is the tank, occupied with water; bb two iron columns, with pulley-wheels on the top; cc chains attached to a ring of iron, dd, extending round the gasometer, which chains pass over the pulley-wheels, and are loaded at their extremities, for the purpose of balancing the weight of the materials of which the gasometer is composed.

The gasometer is formed by several cylinders, sliding one within the other, as the tubes of a telescope; eee is the first or outer cylinder, closed at the top, and having the ring of iron, d, passing round it, by which the whole is suspended; ffis the second cylinder, sliding freely within the first, and there may be a third and fourth within these if necessary.

When there is no gas in the apparatus, all the cylinders are sliden down and remain one within the other immersed in the tank of wa

ter; but when the gas rises through the water, pressing against the top of the gasometer, its levity causes the cylinder, e, to ascend. Round the lower edge of this cylinder a groove is formed by the turning in of the plate iron, and as it rises, the edge takes hold of the top rim of the cylinder, f, which is overlapped for that purpose. The groove at bottom of the first cylin

der fills itself with water as it ascends, and by the rim of the second cylinder falling into it, an airtight hydraulic joint is produced.

Thus several cylinders may be adapted to act in a small tank of water, by sliding one within the other, with lapped edges forming hydraulic joints, and by supporting the apparatus in the way shown; the centre of gravity will always be below the points of suspension. A gasometer may be made upon this plan of any diameter, as there will be no need of frame work, or a bridge to support it, and the increasing weight of the apparatus, as the cylinders are raised one after the other, may be counterpoised by loading the ends of the chains, cc.

Large cast-iron tanks upon the old plan, and the bridges for suspending the gasometers, are extremely expensive in erecting; and in London and other populous neighbourhoods, where dwellinghouses are closely contiguous to the works, great inconvenience would arise from deep reservoirs. of water. Both these disadvantages are obviated by Mr. Tait's improved gasometer; and the capacity of one very large vessel, or of several vessels, may with perfect convenience be obtained by these means within very contracted premises. From the London Journal of Arts and Sciences.

THE LEAD TREE. (From a Correspondent.) PROCURE a and fill it with spring waters to phial or decanter, which add a small quantity of su gar of lead, (about one ounce of lead to a quart of water,) then to a piece of zinc fasten a wire crooked in the form of a still; fasten the zinc in such a manner to a cork that the wire hangs downwards; immerse this into the fluid, and in a few hours the tree will begin to grow, and produce a most beautiful effect. izvaken

B

A

METHOD OF DETECTING

LEAD IN WATER. WHEREVER water kept in leaden vessels is allowed to come into contact with air, the lead becomes oxidated; and though the water has no direct action on the lead itself, it has on this oxide,—it dissolves a portion of it and becomes poisonous. Every body knows of the fatal disease to which those people are subject who are much employed about lead works. Lead, therefore, is a poison; and as water is very frequently kept in leaden reservoirs, it becomes of great importance to the health to have a means of detecting it. So many instances have occurred of whole families having been made unwell by using water impregnated with lead, that we earnestly recommend our readers, whenever they have the least suspicion that the water they use contains lead, to make use of the following test:-Take a bottle, A, to which adapt a cork furnished with a glass tube, B, bent at right angles. Take one part by weight of sulphuret of antimony, break it into pieces the size of a pin's head, put it into the bottle, and pour on it four parts by weight of muriatic acid; then put the cork with one end of the tube into the bottle, and the other end into another bottle or phial, C, containing the water to be examined. Sulphuretted hydrogen gas is disengaged from the materials in the bottle, A, and passing into C, will give the water, in about five mimutes, if it contains the least quantity of lead, a dark brown or blackish tinge. The extrication of the gas may be facilitated by the action of heat. When applied in this manner the most minute portion of lead may be detected.

Remarkable Relation existing between the Crystalline Forms, the Atomic Weights, and Specific Gravities of various Sub

stances.

It is not often that science is indebted to the inhabitants of Russia for improvements; whenever it is, therefore, it is our duty more particularly to acknowledge it. This makes us desirous of noticing a paper, the title of which we have literally translated, lately published in the Annales de Chimie et de Physique, by a Mr. Kupffer; evidently a German, but a professor at the Russian university of Casan; in which that gentleman shows, that there exists a constant relation between the volumes, the specific gravities, and the weights of the atoms of several bodies. This relation he expresses by this equation: Ps

y

p' st

y

(1)

in which p and p' represent the weight of the atoms of two different substances, ss' their specific gravities, y y the volumes of their primitive forms, the half of the diameter being supposed equal to unity. The learned professor then enters into a number of calculations, and describes how accurately he measured the angles of various crystals, to show that his formula gives very nearly the same results as the calculations of the weights of atoms, which have been made according to the atomic theory. Not exactly comprehending this marvellous relation, we merely state it, leaving our readers to draw what instruction from it they

oan.

For ourselves, however, we must observe, and we believe others may be sensible of the same circumstance, that our veneration is always in proportion to our ig norance; that we never worship when we have knowledge; and, like Boniface in the play, who liked Latin all the better for knowing nothing of it, we have a prodigious respect for every thing relative to atoms and their relations, because it is all beyond our comprehension. Q 2