labours of a variety of chemists were instrumental in obtaining the result.

CARBONIC OXIDE. A gaseous compound, consisting, like carbonic acid, of carbon and oxygen, but containing only half the oxygen that exists in carbonic acid, or it consists of 43 carbon and 57 oxygen in 100 parts. It was one of the latest discoveries of Dr. Priestley, and is obtained by subtracting oxygen from carbonic acid. When this oxide is breathed it is destructive of life. Sir H. Davy inspired it mixed with atmospheric air, was severely affected at the moment, and did not recover for several days. Mr. Witter, of Dublin, was struck as by an apoplectic fit from breathing it, but was speedily restored by breathing oxygen.

CARBURETS. Compounds of carbon and a salifiable base.

CARBURET OF MANGANESE, keesh. A substance occasionally met with in iron foundries, being a compound of carbon and the metal.

OF SULPHUR, sulphuret of carbon, alcohol of sulphur. A fluid obtained by distilling pulverized pyrites and charcoal in an earthen retort. It is a compound of sulphur and carbon, and may be considered as a curious illustration of the effects of combination, in changing the nature of substances; for in this case two bodies which are usually in the solid state, form, by their union, a fluid which may be cooled down to 80o below Zero without becoming solid.

CARBURETTED HYDROGEN GAS, bihydroguret of carbon, heavy inflammable air, fire damp. A compound of hydrogen and carbon. This gas exhales in mines and from stagnant water; the gas obtained from coal for lighting the streets is carburetted hydrogen mixed with hydroguret of carbon, or olefiant gas and carbonic oxide.

SPAWNING OF SALMON. SPAWNING is not the only purpose for which salmon leave the sea. They find food in the estuaries of rivers, and they go into the

fresh water to get rid of the sea louse. But those which have been long in fresh water have often their gills almost eaten through with another species of vermin, called maggots.

The following is their mode of depositing the spawn:-"They proceed to the shallow waters, generally in the morning, or at twilight in the evening. They play round the ground two of them together. When they begin to make the fur row, they work up the gravel rather against the stream, as a salmon cannot work with his head down the stream, for the water going into his gills the wrong way drowns him; and when they have made a furrow, they go a little distance, the one to the one side and the other to the other side of the furrow, and throw themselves on their sides when they approach, and shed their spawn into the furrow at the same time. I have seen three pair upon a spawning bed at a time, and have stood and looked at them, both while making the furrow and laying the spawn." They do not lay the spawn all at once, but from time to time in eight to twelve days. When they are done they go into a pool to recruit themselves. About a fortnight or three weeks after this, the male begins to seek his way down the river. The mother fish remains longer, sometimes till the first fry come down, in March or April. He has seen these kelts, or mother fish, with the skin rubbed off below the jaws, in consequence of ploughing up the gravel. The fry come into life from 10th March to 10th April, and in the Tay they have generally all descended to the sea by the end of May. He estimates the number of ova in a salmon to be from 17,000 to 20,000, each of which may become a fish. He holds the herlings of Annan, the whitings of Carlisle, and the finnocks of the north, to be all the same fish, and distinct from the salmon. The grilse also he considers to be quite a different species of fish from the salmon, but similar in their habits. They go up the rivers to spawn,

and come down kelts. The same remark applies to the sea trout. He has taken in one draught, kelt salmon, kelt grilse, kelt trout, and kelt herlings. Evidence of Mr. Halliday, before the Committee on Salmon Fishery.

MUSICAL FISH.

THE following account of a musical phenomenon, supposed to be produced by fish, may not be unacceptable to our readers. It is taken from Lieutenant White's History of a Voyage to the China Sea, and occurred to him at a spacious estuary on the Douai river, in Cochin China:-" Our ears were saluted by a variety of sounds resembling the deep bass of an organ, accompanied by the hollow guttural chant of the bull frog, the heavy chime of a bell, and the tones which imagination would give to an enormous Jews'-harp. This combination produced a thrilling sensation on the nerves, and, as we fancied, a tremulous motion in the vessel. The excitement of great curiosity was visible on every face on board, and many were the sage speculations of the sailors on this occasion. Anxious to discover the cause of this gratuitous concert, I went below, where I found the noise, which I soon ascertained proceeded from the bottom of the vessel, increased to a full and uninterrupted chorus. The perceptions which occurred to me on this occasion were similar to those produced by the torpedo or electric eel, which I had before felt; but whether these feelings were caused by the concussions of sound or by actual vibrations in the body of the vessel, I could neither then nor since determine. In a few moments the sounds, which had commenced near the stern of the vessel, became general throughout the whole length of the bottom. Our linguist informed us that our admiration was caused by a fish of a flat oval form, like a flounder, which, by a certain conformation of the mouth, possesses the power of adhesion to other objects in a wonderful degree, and

that they were peculiar to the Seven Mouths (the part of the river where we then were); but whether the noises we heard were produced by any particular construction of the sonorific organs, or by spasmodic vibrations of the body, he was ignorant. Very shortly after leaving the basin, and entering the branch through which our course lay, a sensible diminution was perceived in the number of our fellow-travellers, and before we had proceeded a mile they were no more heard. On the ship's return down the river, the same submarine serenade again saluted the ears of the crew at the same spot."

EFFECT OF OXYGEN ON GLOW-WORMS.

It is an interesting experiment, (says Mr. Parkes) to place a glowworm within a jar of oxygen gas in a dark room. The insect will shine with much greater brilliancy than it does in atmospheric air. As the luminous appearance depends on the will of the animal, this experiment probably affords an instance of the stimulus which this gas gives to the animal system.

TO CORRESPONDENTS. The request of A Young Admirer of Chemistry has been attended to.

Persons desirous of purchasing a small collection of chemical apparatus cheap, may hear of such, we are informed by a Correspondent, at Mr. Sinclair's, 24, Rathbone-place, Oxford-street.

We shall hereafter notice Tanning.
T. R. S. in a future Number.

If A Subscriber will point out the date of the patent he alludes to, we will attend to the subject.

ERRATUM in Chemist, No. XXVI. page 406, bottom line, for species read weight.

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

London: Published by KNIGHT and LACEY, 55, Paternoster-row.-Printed by B. Bensley, Bolt-court, Fleet-street.

DECOMPOSITION OF WA

TER.

(From a Correspondent.) A is a glass partly filled with pure water; CD, are two tubes, open at one end; ff are two pieces of platina foil; EE are wires attached one to each end of the galvanic trough. The two tubes are held in their places by passing through corks at the top. When put in the position above represented, and the two wires attached to the battery, the products are obtained separately in the two tubes. The wires which pass through the sides of the glass are brass, to which the platina foil is attached; the brass wire must be covered with sealing-wax, as far as the junction with platina, to prevent the brass from being oxidated from the decomposition of the water.

PROFESSOR LESLIE ON LIGHTNING CONDUCTORS. PROFESSOR LESLIE has lately published, in the Edinburgh Philosophical Journal, a paper on Electrical Theories, in which he denies, and very justly, that there is any reason whatever for supposing that an electrical fluid exists. He also endeavours, in an ingenious manner, to account for all the phenomena of electricity, without supposing there is a separate fluid. We are not so certain that his explanation is correct, as we are that his denial of the old theory is well founded. He seems to suppose, that the air is the conducting body, and that what are called currents of the electrical fluid are only currents of air in an electrical state. We shall not discuss the merits of this theory, but lay before our readers what he says of lightning conductors :

"But, whatever speculations we may form in regard to electrical light, and the mode in which the point and the knob produce their different effects, we must admit that the electricity is never communicated, in any perceptible degree, to a remote and unconnected body, but by

means of a current of air;* and this established principle will enable us to estimate the real effects of conductors or thunder-rods.

"When two portions of air, near the point of saturation, and of different temperatures, are mixed, a quantity of the dissolved vapour is precipitated, and resumes its aqueous state. By this conversion the mass acquires electricity; and the consequent repulsion exerted tends to disperse the minute globules of water, which will float in the atmosphere, or rather, will descend with that slow motion which is sufficient to occasion a resistance on their large surface equal to their gravitation. If the cloud+ thus generated reach the ground, it will soon communicate its electricity. If it be suspended at some height, the electrified air will stream from it in all directions; and if its formation be gradual, this discharge may suffice to waste its force. But when a vast cloud is suddenly formed, the aerial emission hardly impairs its electricity; and as it is carried along, it continually approaches, by its attraction, to the surface, which assumes an opposite electricity; the air now rushes with violence, and the cloud berds faster downwards, till at last its lowest verge reaches the ground, and a total discharge is made. The magnitude of the stroke will evidently depend on the extent of the aqueous mass, the suddenness of its precipitation, and the rapidity of its descent.

"The air, which streams in all directions from the cloud, is dissipated among the more remote portions, and thus gradually communicates its electricity. Hence, from the wide dispersion, owing to the distance, the electricity of the air at the surface of the earth must be weak; and, even in the midst of

*The reader will bear in mind, that this is the Professor's theoretical assumption.

It is a common observation in the passed, the wind still blows from the country, that, after a thunder-cloud has cloud, though in an opposite direction.

the storm, the electrometer is less affected than if placed only a yard behind the prime conductor. Yet the action of the thunder-rod is confined entirely to the air which immediately surrounds it, and the quantity of aerial current which it can produce, must evidently be in ferior to what is directed to the point, when held several feet from the conductor of an electrical machine. But to avert the stroke, it would be necessary that the whole air between the surface and the cloud should be brought successively in contact with the top of the rod. Nor is this all; for the air will be constantly replaced by other electrified portions emitted from the cloud. The effect of the thunder-rod is therefore, comparatively, but a drop in the ocean.* It may be easily shown, that, how ever pointed and tapered, it would require a thousand years to guard at the distance of an hundred yards; if terminated with a knob, it might take ten thousand years. Such are the vaunted performances of thunder-rods, and such the advantages of their different forms! +

*It appears, from the experiment with the heated ball, (an experiment to prove that, by means of heat, a ball may be made an equally good conductor with a point,) that a good kitchen fire has more efficacy in preventing a house from being struck, than a whole magazine of thunder-rods. Hence one of the reasons why a thunder-cloud diminishes so fast in passing over a large city.

The utility of thunder-rods not being once questioned, it was yet keenly disputed in England for several years, whether these should be terminated by points or by knobs. But, what is amusing, politics soon came to be mixed up with the controversy. The powder magazine at Purfleet, though guarded by pointed conductors, happening, in 1778, to be struck by lightning, the Privy Council made an application to the Royal Society to investigate the cause of this accident. A Committee was accordingly named of its ablest members, who, still adhering to the hypothesis of Franklin, only recommended additional pointed conductors to be placed at nearer intervals. This Report, in the height of the revolutionary war, could not be otherwise than displeasing to the courtiers, who, from their

Nor can we appeal to experience; it never can be proved that thunderrods have produced beneficial effects, but several instances may be cited where they have afforded no sort of protection.* Nay, we shall be convinced, that fully an equal proportion of the buildings armed with such supposed safeguards have been struck with lightning. But if thunder-rods are useless, they are also innocent; and that they provoke the shaft of heaven, is the suggestion of superstition rather than of science. The cloud exerts an attraction, indeed, upon the surface of the ground, but the force depends solely on the distance, and is not, in the least degree, affected by the shape or quality of the substances below. It rolls towards the nearest and most elevated objects, and strikes indiscriminately a rock, a tree, or a spire.

66

If a thunder-rod be then a harmless, though idle appendage of a house, why awaken uneasy apprehensions? It might at least inspire confidence in the moments of danger; and if happiness consists merely in idea, why not in

losopher, were as eager to depreciate his violent antipathy to the American phiaccordingly set on foot a subscription to science as to deride his patriotism. They enable Mr. Wilson to perform electrical experiments on a large scale in the Panseemed favourable to the theory of knobs. theon, and the conclusions thence drawn The Royal Society was in consequence desired by high authority to revise their Report; but the President, Sir John Pringle, replied with some warmth, that This venerable person, however, being he could not change the laws of nature! worried on all sides, soon resigned the chair in disgust, and retired into the country.

* At the very moment the Professor is so stoutly denying the utility of thunder-rods, some of the suvuns of the French Institute, by the command of the miuister of the interior, have formed themselves into a committee to aseertain the best shape and form for these instruments; and the result of their labours has lately been brought before the public, in a very elaborate memoir, contained in the Annales de Chimie et Physique.