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an ore of iron, and contains as much as 80 or 90 per cent of the pure metal; it is very extensively disseminated over the globe, but is generally found in large masses, in those rocks which Geologists denominate as primitive. The property of the Loadstone for attracting iron, was well known to the ancients, and in several countries this property procured it the appellation of "leading stone, touch stone, stone which attracts iron, the stone of love," &c, names which it still retains.
In almost every country where the loadstone is known it has received a name, indicative of some inherent property in that mineral. We here add a list of nations, with the name of the magnet in the language of the country, and its signification.*
Name of Loadstone.
Iman—Padre de Cevar
The iron stone
Stone of Heracliu
Stone that carries a load or weight
The stone that attracts iron.
The stone that attracts iron.
The sight stone.
From Magnus, the shephered.
Seeing stone, victorious stone, &c.
The leading stone.
The love stone.
From the Greek shepherd Magnus.
The loving stone.
The drawer of nails.
The attractor of iron.
The stone that directs or conducts.
The master of iron.
Stone for rubbing the needle.
The stone for the steel needle.
The stone which shews the south.
The stone which attracts iron.
The stone of enterprise.
The stone which loves.
The devil's, or, wizard's stone.
The magnetic stone.
Attractor and repulser of iron, &c.
This wonderful stone has, therefore, been eminently distinguished above every other kind of mineral, by names given to it by different nations, which at once convey to our minds a sense of some of its singular properties: thus, we find it called the stone, that carries a load, that loves, that attracts, that points out, that directs, that leads, that
* From the British Annual, 1837.
conducts, which shews the south, the nail drawer, the master of iron, the atlractor and repulsor, the stone for the steel needle, the wizard's, or devil's stone, the stone that loves, the kisser, the stone of enterprise, &c. These names were probably given to the loadstone at very remote periods of antiquity; that is to say, before the Mariners' Compass was invented, or before it was known that the loadstone possessed an almost unlimited power of transferring its own virtues to any number of steel bars, without being sensibly weakened in its magnetic intensity. If it had been known to what important uses, magnetised steel bars could be be applied,—as to navigation, to mining, and other important purposes, how many more names might have been added, and every one of them conveying a new application of its principles!
It does not appear that any of the names in the list we have collected, conveys any idea of the loadstone's having been applied to navigation, and yet it is to this wonderful mineral, and its transferable magnetic properties to steel, and the practical application of it, to the steering and conducting of ships (when all other resources fail us,) that we owe the greater part of our knowledge of the world we inhabit, the ocean we have explored, and the intercourse we keep up with the remotest habitable regions!
It was believed that the loadstone fed upon iron! this was by no means an unreasonable supposition, since natural magnets actually acquire additional magnetic intensity by being kept in contact with iron; It is on this principle that loadstones are armed with soft iron, in order to increase their power.
It was seriously believed by the ancients, that if much iron was used in the constructions of their ships, magnetic rocks on the sea shore, might attract the vessels, and hold them firmly attached 1 Who has not read the wonderful adventures of Sinbad the sailor, as detailed in the tales of the "Arabian Nights?" How would Sinbad's historian have managed an iron steam vessel? The moderns as well as the ancients, have ascribed wonderful physical, as well as moral effects to the magnet; its properties have been applied by impostors, in their systems of astronomy, astrology, divination, prediction of future events, divinity, law, and physic; and even in this enlightened age, " mesmerism," is practised and patronised!
The property of a magnet, in communicating a permanent magnetism of its own kind to hardened steel, and the directive power of a freely suspended steel magnetic needle arranging itself in a north and south direction, induced a belief that some mysterious agency in the heavens held the compass needle in the direction of the pole star. It was afterwards considered, that magnetic rocks might abound in the polar regions of the world, and draw the needle in that direction, and some supposed that, the earth itself contained a great magnet in its central parts. The variation of the magnetic needle proved that these views could not be correct, because, if the north star itself had been a magnet, if the rocky regions towards the poles had been formed of loadstones, or, if the earth had held a great magnet in its central part, any of these agencies, if permanently fixed in the heavens, or, in the earth, would not have induced a change in the direction of the compass needle.
It is more reasonable to suppose that magnetism, electricity, and gal
ENLARGED SERIES NO. 9 VOL. FOR 1843. 4 Q
vanism, combine to form a mysterious agency prevailing the world, for electricity has been known to invert or destroy the magnetism of a ship's compass; and by galvanism, needles may be magnetised. We know, comparatively, but little of the internal structure of the earth; the cuttings of the engineer, the punctures of the miner, or, the scratches of those who dig or quarry its surface, have penetrated but a very small portion of the distance between the surface and centre of the earth! We are however, certain that the earth's mean density is greater than that of any rocks known to exist near its surface. Our Geological researches, enable us to assert that the globe contains masses of metals, and metaliferous veins, abundantly disseminated among the stratified and chrystalized rocks, which form its external crust. There is evidence to shew that the central parts of the globe, possess a higher temperature, than its part near the surface; that subterranean fires exist in it; and that the masses of matter composing our planet, may be regarded as a galvanic arrangement, its solid parts being connected or covered by an ocean of brine. There are chemical formations, as well as decompositions, constantly going on in it, and the electrical, magnetical or galvanical currents we witness, may result from the physical structure of our earth. If we adopt this view of the globe's being a galvanic mass, many difficulties in our magnetical speculations may vanish, for example, the changes in the daily variation of the compass; and the great change that has taken place in this variation, during the last 260 years, may have arisen from changes in the internal, or external temperatures of the earth, in its various parts, as in Greenland and elsewhere.
It is still believed by many, that iron or steel are the only substances susceptible of magnetism; whereas every known substance is more or less susceptible of magnetic action. Mr. Barlow found that the brass box of a very fine compass with which he had been making experiments, had acquired a permanent magnetism. Mr. Harris* in his paper on the transient magnetic state of which various substances are susceptible,+ has given the following table of the comparative magnetic inductive susceptibility of the following substances.
Mr. Harris found that by condensing the metals, their magnetic energy was increased, and that all substances receive or take up magnetism more rapidly than they part with it. The above conclusions were drawn from experiments, made on metals subject to the action of
The talented author of the papers on Electricity, in this journal, and to whom we. a„? "xlebted for an efficient method of protecting our shipa from lightning, t Philosophical Transactions, 1831.
artificial magnets vibrating within discs, or rings of the metals, included in the above table.
Professor Whewell in his Bridgewater Treatise, "on the power, wisdom, and goodness of God," (p. 113,) has remarked, "when we consider the vast service which magnetism is to man, by supplying him with the Mariners' Compass, many persons will require no other proof of this property being introduced into the frame of the world for a worthy purpose. Magnetism he adds has been discovered in modern times, to have so clear a connection with galvanism, that they may be regarded as different aspects of the same agents; all the phenomena we can produce with magnetism, we can produce with galvanim. That galvanism exists in the earth, we need no proof. Electricity which appears to differ from galvanism, the same manner in which a fluid in motion differs from fluid at rest, appears to be galvanism in equilibrium; and recently Mr. Fox* found by experiment, that metaliferous veins, as they lie in the earth, exercise a galvanic influence on each other. Something of this kind might have been expected from masses of metal in contact; if they differ in temperature, or, in other circumstances, are known to produce galvanic currents; hence we have undoubtedly streams of galvanic influence moving along the earth, but whether or not such causes as these produce the directive power of the magnetic needle, we cannot here pretend to decide; they can hardly fail to affect it."
The opinion here given is from high authority, and I cordially agree to it. The whole of the materials forming a ship are susceptible of magnetism by induction from the earth, the sea, and the atmosphere; the mechanical construction is such, that the whole fabric of the ship may be in a transient magnetic state, not only the iron, copper, lead, brass, and the other metals; but, also, the wood forming the hull, fastened or covered as it really is with these metals and their oxides. Need we then be surprised when we find the steering compasses deviating from the true direction of the magnetic meridian, or, vibrating several points on each side of the course, when a vessel rolls from side to side.
. . (To be continued.) t . .
On Bar Harbours.—By Mr. E. K. Calver, master H.M.S. Blazer.
The whole of the ports along the Eastern Coast of Great Britain, from Father Thames to John o'Groats, may be classed, with one or two exceptions, under the head of Bar Harbours. Some remain in the state determined by nature; others have undergone alteration by the erection of piers, sluices, breakwaters, &c, having for their object the removal of some existing evil. In one or two instances the effect produced has been favorable, in others the advantage is problematical; but, in the majority of cases, the intended remedy has proved worse than the disease, entailing, as a consequence, accumulated difficulties; a fact, suffi
• Of Falmouth, in Cornwall.
went of itself to prove, that the projectors cannot possibly have been guided in their operations by any established law of cause and effect. , Th* f?,lowing haS suSgested itself to rae uPon this interesting subject, though it will be seen that my sphere of action is very confined, as it only embraces, within its limits the cases of those rivers whose waters meet the ocean nearly at right angles.
Plan of Harbour Improvements.
From a quarter of a mile above the junction of the river with the sea, gradually narrow its downward course, by embankment or otherwise, as most convenient, taking care that the divergence of the sides be not so great, as to cause the velocity of the outset at the entrance to exceed the rate of five miles per hour. The piers would be a prolongation of the river embankments, with the position of their extremes determined by the local conformation, &c—(See following sketch.)
A to B, limits of operation.-C to D, embankments.-E to F, high water Une.-G to H low wawr line.—K, capstans on Pier Head with warping posts.
For the application of this principle, let us take for example three rivers, whose breadth, and mean sectional depth at a quarter of a mile above their entrances is 500 feet and 9 feet respectively, but the rale of tide at half-ebb is severally one, two, and three miles per hour. Now, as the velocity of the outset must principally depend upon the conductor it has to pass through; and, allowing that the first effort of the contraction would scour the bottom between the pier-heads one-third lower from a mean level, the breadth of entrance proper in each case is arrived at by a simple proportion,—to attain the specified velocity of five knots in the above instances it would be roughly 70, 140, and 200 feet.
Thus, in all cases, estimating the capacity of a river by its breadth, depth, and velocity, at a given distance from the sea, the width of entrance proportioned to it in accordance with the foregoing principle. may at once be arrived at.
Results to be expected.
The advantages to be gained by this arrangement are numerous, though I shall briefly advert to the following, as among the most important:— *
1. If the above plan, or any other having the same object in view, be found equal to the ordeal of a practical test; the mistakes which are daily committed in one section of marine engineering will be avoided,