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Sir, I often wonder that among all the expeditions of enterprize to the Frozen Regions there never has been one made with vessels constructed for the express purpose. I have never yet seen nor heard of a ship being built for such an expedition:-that is to say, adapted in every circumstance of its structure to the peculiarities of the Polar Regions. It is a well known fact, that the destruction of so many ships in the Frozen Regions has been occasioned by the ships' sides being too upright, or by the ships being narrower over the main deck than lower down at the surface of the water, when the ship is in ballast trim. To illustrate the truth of this remark I shall relate one occurrence out of the many that have happened of this description.

In the year 1819, (to the best of my recollection,) there happened in Davis's Straits as great a shipwreck as any on record. There were two large floes of ice that lay at a considerable distance from each other; the one was drifted up against the land, and the other was drifting off at sea. The wind shifting suddenly round, drifted the large body of ice at sea in upon or against the other body of ice that lay along shore. To this last there were a

number of whaleing vessels made fast, and not having time to get out of the way, thirty-two of them were crushed to pieces or destroyed in the space of twenty four hours. Two, however, were saved, with which I was well acquainted. The first was the William and Ann of Leith, (in which I sailed the year before.) The most projecting part of the ice happened to catch her just below the bilge of her sides, and raised her above the ice till the crew saw her keel. The other ship was saved in the following manner: The crew took the large anchors and hoisted them up towards the main top, to make the ship top heavy; then with ropes made fast to the main-topmast, cross-trees, &c. they hauled the ship down almost upon her broadside, against the ice, till the opposite ice got underneath her bottom and squeezed the ship entirely upon the top of the ice, out of the water. In this state she lay till the wind again separated the ice, and she sunk in open water.

Now to prevent such disasters in future, I would propose that ships built for the service of the frozen seas should have shifting sides and keels, in the manner represented in the accompanying drawings.

Fig. 1. Represents a ship beset between two large floes of ice, with her sides spread out to make the ship rise out of the water, as the ice sets in hard upon her. The keel is exhibited hoisted up, and level with the bottom, to prevent it from being carried away.

Fig. 2. Represents a ship in open water, free of danger, her sides up, and keel down to its proper place.

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Fig. 3. Represents a ship beset between a large floe of ice on her left, and a large iceberg on her right, her left side spread out, to make the floe go underneath her, and her right side hauled upright, to make the iceberg squeeze the ship upon the top of the floe.

Fig. 4. Represents the naked keel, with the necessary apparatus for hoisting it up and down

I may here add a tew remarks as to the nature of the frozen regions, which will develope another cause of our late adventurers making so many voyages of discovery to no purpose. In the Old Greenlands, the currents in general run to the north, and carry the ice, &c. along with them. In the New Greenlands, or, as they are com monly called, Davis's Straits, the tides run always to the south, and carry the ice along with them to the Atlantic Ocean, where it generally dissolves. In Old Greenland, the ice is generally all in thick floes, packs, or streams, or the like. In New Greenland, the ice seldom gains such enormous thickness, as that which is commonly to be met with in the straits. Although it is considered a great deal colder in the New Greenland, the ice is to be met with in all sorts and sizes, shapes and forms, from one inch in thickness, to a thousand feet, and is nothing thought of at that. The causes of this great difference, I conceive to be these.In the first place, at the beginning of winter, the waters begin to freeze

at Old Greenland, and keep gradually going to the north with the current of the tides, and increasing in thickness till they reach what we may call the Pole, or the region of extreme cold; when summer returns, a perpetual sun acts with such intense force upon this immense body, that it is broken in pieces-falls into the current of the straits, or New Greenland, and comes down to the south with the tide, into the western ocean, having the appearance of mountains, islands, castles, &c. It is evident, therefore, that one chief cause of the bad success of our adventurers is, their going by the route of New Greenland-they have the tides, all the ice of New Greenland, and all the ice of Old Greenland, coming against them. Now, I would recommend, that were a ship built according to the plan I have given above, it should enter in at Old Greenland in the beginning of summer, follow the courses of the tides and the ice, winter at the Pole, and come down with the tides and the ice by Davis's Straits the following summer; which

think it might do, with all manner of safety and certainty of success. I remain, Sir, &c..

A Subscriber, and an Old Adventurer in the Frozen Regions.

ELECTRICITY AND MAGNETISM.

(Abstracted from an article in the last number of the Quarterly Review.)

Electricity and Magnetism were, for a long period, considered as constituting two distinct departments of physical science. From all the direct experiments, indeed, that were made prior to the time of Ersted, (to whom the merit belongs of originating the new science of electro-magnetism,) no other conclusion could be deduced than that electricity and magnetism were powers totally independent of one another, although marked by characters of similarity in their modes of action.

'The question as to the identity of the two agencies, was proposed as the subject of a prize dissertation, by the Aca demy of Bavaria, as far back as 1774; on which occasion, several elaborate memoirs were drawn up by Van Swinden, Steiglehner, and Hubner. A collection of these memoirs was published, ten years afterwards, by Van Swinden, containing a large mass of materials, from which some valuable facts may be gleaned.

That some connexion actually exists between electricity and magnetism, was proved by a great variety of circumstantial, at least, if not direct evidence. It was observed that lightning, on some occasions, rendered the iron which it met with in its passage, magnetic. This effect had sometimes, also, resulted in experiments, in which steel bars had been made the channel for the discharge of artificial electricity, especially when powerful batteries were employed. But the success of the experiments made with this view, was by no means constant (uniform); they of ten failed of producing any magnetism; and still less could any certain conclusion be established with respect to the particular polarity which each species of electricity tended to produce. When magnetic compass needles were subjected to the electric discharge, their power was often weakened, and sometimes de stroyed, and the poles of the needle were occasionally found to be reversed by

the operation; so that if the needle were suspended on its centre, that end, which before turned towards the north, now pointed towards the south, and

vice versa.

A similar effect has been known to result from lightning when it passed near to a ship's compass; and many stories are related of disastrous accidents arising from this cause.

Certain phenomena there were, which appeared to afford a plausible solution of the difficulty. It was well known that the globe of the earth exerts on all ferruginous bodies, an influence similar to what would arise from a powerful magnet, situated near to its axis. Iron has, in consequence of this influence, atendency to acquire spontaneous polarity; the direction of the poles of iron so affected, being the same with that assumed by the dipping needle; that is, by a magnetic bar suspended accurately on its centre of gravity, and allowed perfect freedom of motion, not merely in a horizontal plane, (as is the case with the compass needle) but, also, in a vertical plane. The direction it will then assume in London, is a line inclined 7010 to the horizon; and the lower end decreasing 24° to the west of the meridian. If a bar of steel be held in this position and struck repeatedly with a hammer, or if it be heated red hot, and then suddenly cooled by immersion in water, while in this same position, it will be found to have acquired permanent magnetic properties. That end which was nearest to the north mag-. netic pole of the earth, will have acquired the property of directing itself to the north, when suspended, so as to allow of its moving freely in a horizontal plane; while the other end will have acquired the opposite polarity. It was, therefore, natural to conclude that it was merely by its mechanical action, that the electric discharge induced magnetism, in those instances where it was found to have this effect. The electricity was supposed to operate, by giving to the particles of the solid body, the same kind of vibratory motion, which is produced by any other mode of concussion, whereby the inductive influence of the earth's magnetism was promoted.

Such were the imperfect notions universally entertained on the subject, not only in the time of Van Swinden, but down to the period of the discovery of galvanism. The extensive field of enquiry laid open by this discovery, wa explored with ardour, by philosophe

in every part of Europe. It was sometime, however, before the real nature of the galvanic influence was perfectly ascertained; and a long controversy arose on the question, whether it was a mere modification of electricity, or a distinct and peculiar power. But all doubt as to its identity with electricity was at length removed, by the splendid discoveries effected by the voltaic pile and battery, and the successful imitation of some of their effects, by means of common electricity, which was accomplished by Dr. Wollaston.*

[To be continued in our next, when we shall give the Reviewer's views of the distinctions which characterize the different forms of electricity and galvanism.]

MR. VALLANCE'S NEW MODE OF CONVEYANCE.

(Report of Chevalier Couling, con

cluded from p. 39.)

"Sixthly, A degree of exhaustion, or vacuum, which is not sufficient visibly to affect the barometer, being enough to move the carriage with persons in it, so as for them to experieuce the effect, and fully comprehend the operation of the principle, it becomes evident that the idea at first entertained of a perfect vacuum being indispensable, is most erroneous; and the objections which at first present themselves to us, relative to the difficulty of constructing the cylinder, of making the joints airtight, and of so adapting the ends of the vehicle to the cylinder, as should prevent the passage of any important quantity of air, without occasioning great friction, are all seen to exist only in imagination. In the cylinder which Mr. Vallance has in operation at Brighton, there is a space of above an inch in width, purposely left all round between the cylinder, and the end of the carriage which forms the piston, against which the air presses to drive the carriage along; yet does not the air which rushes through this crevice (though it is in the whole equal to an aperture of two square feet), prevent the operation of the * Philosophical Transactions for 1801, p. 427.

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principle; its sole effect being a loss of a proportion of the power employed to drive the air-pumps; a loss which Mr. Vallance intentionally submits to, for the sake of proving that a very large portion of air may rush by the piston end of the carriage, without preventing the effect of the principle. Vide pages 30 and 31.

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Seventhly, nor will the degree of which it may be necessary to exhaust, or, as it may in other words be termed, the degree of vacuum' required, interpose any insuperable difficulty. to move even a very great weight, In the cylinder at Brighton, a party, consisting of his Grace the Duke of Bedford, the Earl of Lauderdale, Lord Holland, Lord W. Russell, Lady W. Russell, and another Lady and Gentleman, were all at the same time experiencing the operation of the principle, on the day I was last at Brighton, with a degree of exhaustion not exceeding two drachms per square inch; a proportion of vacuum which would lower the barometer about one-hundredth of an inch. Practice, therefore, proves, as well as the arguments in pages 47 and 48, that a very trivial degree of exhaustion will be sufficient to move a considerable load; and as it will be perfectly practicable to exhaust to a degree, that should render a barometer exposed to the vacuum inside the cylinder, several, if not many inches lower than one would stand exposed to the atmosphere, I do not think the amount stated in page 37 more than it may be possible to move at one time. And with reference to weights of 50 or 100 tons, such as loco-motive engines draw at once, there will certainly be no difficulty at all, let the velocity they are moved at be what it may.

Eighthly under the trivial degree of exhaustion which will thus, generally speaking, be necessary, your Royal Highness will perceive, that rendering the cylinder sufficiently air-tight for the purpose, will be far less difficult than it is at first supposed. Indeed, I see so many different ways of doing it, that I am satisfied it would not, in practice, prove more difficult, nor indeed so difficult,