Adapt a bent glass funnel to the opening at A, making it air tight, either by grinding, or by passing its end through a cork, which shall fit the opening, Plunge the beak of the retort under water in a pneumatic apparatus, and pour through the bent funnel about twice as much sulphuric acid by weight, previously diluted with four times its bulk of water, as there is iron filings in the retort. Immediately the diluted sulphuric acid reaches the iron filings, the mixture begins to boil or effervesce with violence, and bubbles of air escape rapidly from the mouth of the retort. After allowing as large a quantity to escape as you suppose will have supplied the place of the atmospheric air contained in the retort, place an inverted glass jar on the pneumatic shelf (see No. II) over the beak of the retort; and the gas which will soon fill it, displacing the water, is hydrogen gas. It may also be procured in great abundance by causing the steam of water to pass through a red hot iron tube. This is done by placing an iron tube, part of a gun-barrel, for example, in a furnace, allowing the two ends to project, one on each side of the furnace, and placing it so that the narrowest end shall be somewhat lower than the other. Adjust a small glass retort to the upper end, and to the other a tube, the end of which must be introduced into the pneumatic trough. When the apparatus is thus ready, and the barrel is made red hot, bring the water in the retort to boil, and the steam passing through the red hot iron will be decomposed, and yield an abundance of hydrogen gas. For researches in which great accuracy is required, it must be received in jars over mercury, and exposed to the action of dry muriate of lime at a low temperature. By this means it is freed from water, which it otherwise holds in solution. Being sometimes emitted in considerable quantities from the sure face of the earth in mines, it very soon attracted the attention of che mical philosophers. Mayow, Boyle, and Hales procured it, made experiments on it, and observed some of its mechanical properties. About the beginning of the 18th century, its combustibility was known, and was often exhibited as a curiosity. But it was Mr. Cavendish who, in 1766, first pointed out the difference betwixt it and atmospheric air, and ascertained the greater number of its properties. He is therefore to be considered at least as having discovered most of its peculiarities. Since his time it has been investigated by a great number of chemists, and from their researches the following facts are fully established. Hydrogen gas, like air, is invisible and elastic, capable of being compressed, and endowed with a property of dilating itself. It is the lightest body with which the researches of chemistry have yet made us acquainted. If the specific gravity of atmospheric air be assumed as 1.000, the specific gravity of hydrogen, at a temperature of 60 Fahr., and when the barometer is at 30 inches, is 0.0694. 100 cubic inches weigh 2.118 grains. It is therefore about 14 times less dense than common air, and 16 times less dense than oxygen gas. From the lightness of this substance, it is employed for the purpose of inflating balloons, which, when filled with it, rise rapidly through the denser atmospheric air. For a very long time it was supposed to be totally incapable of supporting combustion; but the circumstance mentioned in our No. III, relative to platinum, makes this negative attribute of hydrogen gas doubtful. We do not say that the phenomena of the platinum becoming red hot when a stream of hydrogen gas is directed on it may not be otherwise explained, but till it is, it would be wrong to assert that hydrogen is in no case a supporter of combustion. In fact, this sort of phraseology is altogether derived from a theory which is already partly overthrown, and may, perhaps, be ultimately entirely demolished. Combustion, in correct language, only signifies that particular che mical changé, decomposition of some bodies and the formation of others, which is accompanied by the emission of light and heat; and although the co-existence in the same spot of two certain substances is necessary to the production of this phenomena, it does not appear to be yet proved which of the two, or if both give out light and heat, and consequently it would be as correct to call the bodies, now named supporters of combustion, combustibles, and vice versa, as the contrary. If, as has been stated, sound logic would justify us in calling oxygen, chlorine, and iodine combustible bodies, it would equally justify us in calling hydrogen a supporter of combustion, for no body is more inflammable. In fact, its readiness to take fire procured for it, in the first instance, the name of inflammable air, and of phlogistion, or the principle of fire. If a lighted candle be brought to the mouth of a jar filled with hydrogen gas, the gas will take fire, and burn gradually till it is all consumed; but if the candle be plunged in the gas, it is extinguished. If the gas be pure, the flame is of a yellowish white colour, and if not pure, is tinged of different colours, according as it holds different matters in solution. A red hot iron will set fire to hydrogen, and it is estimated to take fire at about the temperature of 1000. If a bottle containing the sulphuric acid and iron for the production of hydrogen be shut, with a cork having a long straight tube of a small diameter, the hydrogen issuing in a jet, and being set on fire, forms the philosophic candle of Dr. Priestley. If a long glass tube be held over the flame, its sides will be speedily covered with moisture, and harmonic tones will soon be heard. For a long time it was supposed that this was peculiar to hydrogen, and arose from the aqueous vapour; but Mr. Faraday has lately shown that carbonic oxide produces the same sonorous effect. It has been found, also, that the tones produced are different as the shape of the tube or glass vessel held over the flame is different. If pure oxygen and hydrogen be mixed together, they remain unaltered; but if a lighted taper be brought into contact with them, or an eletric spark made to pass through them, they unite with great rapidity, and a violent explosion'; and if they have been mixed in the proportion of one measure of oxygen and two of hydrogen, they are converted into water. This important experiment was first made by Scheele, but he failed to draw from it the proper conclusion. Mr. Cavendish ascertained that the water deposited was equal in weight to the gases which had disappeared, and hence he inferred that water was formed by their combination. This inference has since been confirmed by numerous experiments, and hydrogen received its name from being one constituent of water. Hydrogen gas cannot be breathed without destroying life; and death is caused by depriving animals of oxygen, in the same manner as they would be destroyed if kept under water. Hydrogen gas is not sensibly absorbed by water, and therefore it may be collected over that fluid. In consequence of its combining with a specific proportion of oxygen gas, hydrogen is employed as an eudiometer, or means of measuring the quantity of oxygen gas contained in any given bulk of an elastic fluid. A determinate quantity of hydrogen is mixed with a determinate quantity of the air to be tried, and the mixture is inflamed by an electric spark; the diminution of the volume beyond the quantity of hydrogen employed, indicates the quantity of oxygen contained in the gas. A number of ingenious instruments and contrivances are, however, employed for the same purpose, which will hereafter be described. HABITS OF SALMON. THE discussion now going on in Parliament relative to the salmon fishery, has called forth a number of papers on the subject; among which, one published by the Rev. Mr. Fleming, contains some curious remarks on the habits of this fish, which are worth quoting in a scientific journal. He confines his remarks to the fisheries of the Tay, which, he says, may be divided into the river-fisheries, and the fisheries of the Frith or sea-fisheries; and this distinction is of importance in adopting the most successful methods of capture. Salmon, though inhabitants of the sea, approach the shores, enter our large rivers, and mount upwards to their source for the purpose of depositing the spawn in their gravelly beds. As soon as this object is accomplished they retire again to the sea; and evidently to great depths, remote from cod and haddock ground, to recruit their exhausted strength, and prepare for future efforts of the same kind. Before beginning their journey, they are in a good condition, the body being loaded with fat, as a magazine for supplying the wants of the fish during migration, and for furnishing the great quantity of matter requisite for the evolution of the spawn. When the fish enter the Frith, at the commencement of their upward migration, and are thus in good condition, they are termed, in the language of fishermen, clean fish. At this period they are infested with the salmon louse, caligus productus of naturalists, and which chiefly adhere to the more insensible parts. When arrived at the place of spawning, the fish is lean, as the whole fat of the body has passed into the melt and roe. In this state they are termed red fish, and are worthless as an article of food. After the fish have spawned they are termed kelts or foul fish, and are equally despised with the red fish. The gills are now more or less covered with entomoda salmonea. The motion of the fish upwards from the sea to the river and place of spawning, is influenced by several causes. When there is abundance of fresh water in the Frith, the fish seem to proceed res gularly and rapidly up the middle of the stream, enter the rivers, and hasten to their destination. Under these circumstances it is probable that the ripening of the spawn is accelerating by the influence of external circumstances. When the rivers are but scantily supplied with water, the fish which have entered the Frith, roam about in an irregular manner, influenced by the state of the tide, while those which have been surprised in the rivers by a draught, betake themselves to the deepest pools. In returning to the sea, after spawning, the fish seem to keep the middle of the stream in the river, and the deepest and saltest water in the Frith. Salmon enter the river and Frith at all seasons of the year, but they approach in greatest numbers during the summer months. Fish taken in May, June, and July, are much fatter than fish in the same condition as to spawning, taken in February, March, or April. They fall off in fulness very rapidly from August to January, when they are leanest. The principal spawning season is in November, December, and January. The roe becomes perfect, and the young fry samlets, or smelts, make their appearance in March or April. When the samlets leave the gravel where the spawn from which they issued had been deposited, they begin to move downwards to the sea. In their progress through the river, and until they reach that point where the Frith begins, or where the tide is always either ebbing or flowing; they crowd together and descend in the easy water at the margin. But upon entering the Frith, where the easy water is not at the edge, they betake themselves to the deepest part of the channel, and along with the kelts, disappear from observation. VEGETATION AT DIFFER ENT HEIGHTS. ALL our readers know that all sorts of plants have different homes; some are natives of the sandy desert, some affect salt wave, and some spring up only on the verge of eternal snows. This remarkable attachment to localities is particularly observable in mountainous countries, where we find grouped in a small extent, the productions of the icy north, and of the burning south; there the pomegranate, the orange, and the vine flourish in the sheltered valleys; a few yards above them, and the sides of the hills are ornamented with oak, beech, and birch; higher up, we meet with pines, and, finally, we come to the spot where lichens and moss mingle with the snow. So regular is the progress, and so precise are the heights at which plants will grow, taking the latitude of the place into consideration, that circles of vegetation have been constructed, showing at what heights the different plants may be found cultivated throughout the globe. In connexion with these general results, tables of the heights where different vegetables are actually found, have an additional interest; and we therefore conceive the following table of the various heights at which different trees and shrubs grow in the Vallais and Savoy, worthy of being transferred to our pages. The extreme height implies situations open to the south and west, and sheltered from the north-east wind, the height vary ing very much, according to the aspect in an alpine country. The heights are English feet above the level of the sea, and the latitude 45° 36' to 46° 30'. Mountain Maple... 5100 5500 6000 6300 ...... 6600 ..... Silver Birch.. The line of trees reaches the height of 6700 feet, the line of shrubs 8500. Some plants on a granitic soil grow at 10,600, above which are a few lichens, but vegetation ceases at 11,000 feet. In the garden of the inn kept in summer at the Schwarrenbach, on the passage of the Gemmi, carrots, spinach, and onions are cultivated. at the height of 6900 feet. In the southern part of Savoy, the height at which pines will grow is about 2600, but near this elevation the crops failed in the cold summer of 1821. TO CORRESPONDENTS. The communication promised by a Chemist, we shall, we believe, be able to procure. We thank A Constant Reader for his letter, and his communication shall be inserted.. C. A. D. we take to be a Lady, and shall be extremely happy to insert the paper she promises us. We beg leave here to remind all our Correspondents, that communications from the other sex, on any subject, but particularly on botany, will be very acceptable. Crucible has been received; we shall probably put him on in our next. Though we frequently read the work to which ANTI-STAHL alludes, we did not see the Article he mentions; and, if it were not now too late, we must beg to be excused noticing it, as we do not wish to take on ourselves the task of criticising every Periodical. Communications (post paid) to be addressed to the Editor, at the Publishers'. London: Published by JOHN KNIGHT and HENRY LACEY, 24, Paternoster Row. B. Bensley, Bolt-court, Flect-street, London. |