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USES OF SALT IN MANUFACTURES AND AGRICUlture.

inches thick, I divide the square inches by 2 instead of 4, and so on according to thickness.

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Important advantages are now derivable from salt, since it can be procured without duty. In a work published at New York, by Dr. Rens selaer, some of the purposes to which salt may be applied are thus described :

Sal ammoniac, or muriate of ammo

is made in abundance from common salt. The manufacture of this article was abandoned in England, in consequence of the heavy duty of 307. per ton laid on salt. In consequence, however, of bittern, from the salt works, being allowed in Scotland for the manufacture, the price has been reduced nearly one-half.

In the manufacture of glass, salt is largely employed: soda, which is procured from common salt, is used for plate-glass; potash, for flint-glass; and common salt, with kelp, for crownglass.

Oxymuriate of lime, and other oxymuriatic salts employed in bleaching, are made from salt, and consume a large quantity of it in the manufac

ture.

Spirit of salt, or muriatic acid, requires large quantities of salt: at least 1000 tons are used for this purpose in England every year, notwithstanding the enormous duty. It is used in a variety of processes in dyeing and calico-printing.

Glauber's salt is made from what remains in the stills after the distillation of muriatic acid. This residuum was formerly thrown away, until a person employed it in making Glauber's salt, when a duty of 301, per ton was

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laid on the article manufactured, since, however, remitted.

Epsom salt is produced entirely from salt, or the evaporation of sea water. The brine, which yields 100 tons of salt, gives from four to five tons of this valuable article. Dr. Henry, the celebrated chemist of Manchester, has discovered a process of preparing it from magnesian limestone, and has reduced the price one-half. It can be made still cheaper from sea water, for the employment of which a duty is laid.

Magnesia is made from salt brine, or sea water. The English duties are so high as to render it probable that both this and the preceding article will, in future, be obtained by Henry's process from magnesian limestone.

Crystallized soda is also made from common salt; aud if the latter, or sea water, could be obtained free of duty in England, it would supersede the importation of American or Russian pot and pearl ashes, and 10,000 tons would be used annually, several hundred tons in washing alone.

Barylla, of an excellent quality, is made from salt.

In the manufacture of hard soap salt is a necessary ingredient.

Corrosive sublimate is always made from common, salt.

Patent yellow is also prepared from common salt.

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In the Fisheries, in salting provisions for the sea service and for exportation, salt is largely employed.

Butchers, morocco dressers, and skinners, employ it in large quantities.

[Dr. Rensselaer here calculates that, in England, three times the present quantity would have been eaten if there had been no duty.]

Farmers use great quantities in making butter and cheese, and for steeping wheat to prevent smut.

In glazing earthenware much salt is consumed, and is far preferable to the preparations of lead, which are liable to be dissolved by vinegar and eaten. In England the manufacturers of earthenware sometimes pay one-twelfth of of the real amount of their sales for salt.

Salt is likewise employed by ironfounders in metallic cements, and in rendering har iron very malleable. It is used by whitesmiths and cutlers in

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PROTECTION OF COPPER SHEATHING.

case-hardening, in tempering files and some other edge-tools; mixed with other substances, for reducing metallic ores, assaying minerals, and rendering metals fusible, by the refiners of silver, and to prevent the oxidizement of some metals. It is used to moderate the flame of combustible bodies, and is extensively employed by the philosophical and manufacturing chemist, and by the druggist for a variety of pharmaceutical purposes.

In horticulture salt is much used, particularly in England, where its merits are better appreciated than with It prevents the depredations of insects on fruit trees, and, when properly applied, protects them from the honey dew.

11s.

Persons ambitious of

having good cider orchards should dig a small trench a few yards from each tree, and place within it a few pounds of salt, which by the rains is gradually conveyed to the roots, and produces most desirable effects.

PROTECTION OF COPPER SHEATHING.

At a recent meeting of the Royal Society, there were read, "Further Researches on the Preservation of Metals by Electro-chemical Combinations; by Sir Humphry Davy."

In this paper Sir H. Davy enters into a minute detail of the causes which operate in producing foulness, as it is called, or the adhesion of weeds and shell-fish to the copper of 'ships. This he attributes to a crust of carbonate and submuriate of copper, and carbonate of lime and magnesia, which gradually fix upon the sheathing, and which, by rendering the copper in the surrounding parts positive, occasions its corrosion, so that ships are sometimes found, in the common course of wear, foul in some parts, and the copper worn in holes in other parts.

He conceives that proper protection, if not in excess, by producing a similarity of electrical state, or of 'disposition to chemical change in every part of the copper, will prevent the rapidity of its wear without giving it any disposition to foulness; but if iron or zinc are used in such quantities as to save all the copper, then they will increase the disposition

of that metal to become covered with weeds and shell fish, except in cases of rapid motion, such as in steam boats, where the chemical action of sea water upon copper may be entirely prevented without the possibility of the copper becoming foul.

The President describes a number of experiments, which show that the most rapid motion does not interfere with the principle of protection. Hẹ ascribes the relations of this property of electro-chemical agency to the conducting powers of metals and of fluid conductors; and he shows that a certain contact with fluid conductors, even upon a small scale, is sufficient to enable oxidable metals to preserve more difficultly oxidable metals, and that slight chemical changes are sufficient for the effect. Iron in a solution of brine which contains no air is very slowly acted upon, and yet iron in brine in one cup will preserve copper in sea water in another cup, provided they are connected by a moist thread of cotton. He points out the limits to this kind of action, and illustrates it by a very curious experiment. If of two vessels containing salt and water connected by moist cotton, and forming an electro-chemical series by means of zinc and iron, a few drops of solution of potash or soda be poured into that containing the iron, the action of the iron on the sea water will be diminished, but the copper will still be protected; but if the solution containing the iron be made alkaline to any extent, the copper will begin to corrode, and the iron will become the electro-negative metal.

Sir Humphry ends this paper by the important practical conclusion, that copper may be preserved by nails, or masses of zinc or iron placed under the sheathing, and that, in this way, there is less loss of the oxidable metal, which is partly revived upon the interior of the copper, so that the same metal will act for a long time; and thus protectors may be applied to save the whole or any portion of the copper without interfering with the external surface of it, and without the deposition of any matter likely to cause adhesion.

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KATER'S PENDULUM."

KATER'S PENDULUM.

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then with the other, so that the times of oscillation in both cases are equal, the distance between these two centres will be the length of the equivalent simple pendulum, whatever be the irregularities of form or composition in the instrument. The manner in which this effect was produced was as follows:-A brass pendulum, CD, was furnished with two axles, from which it could be suspended, one passing through C, and the other through O. Besides the principal weight, D, it was provided with a smaller sliding weight, F, which could be moved along the stem, CD; and this weight was to be moved till the number of oscillations, in a given time (as 24 hours), was the same whether the pendulum was suspended from C or from 0. F was placed in such a position, that, by moving it from O as to F, the number of oscillations about C, in twenty-fours, was increased; and by the same change the number of oscillations about 8, in the same time, was still more increased. The adjustment was thus made:-Let the weight be at F, and let the number of oscillations in ten minutes, about C, be 606, and about O be 601; now let F be moved to f, and let the oscillations in ten minutes be 607 about C, and 609 about O (because the latter are more affected than the former); then the proper position of the slider is somewhere between F and f. Let it be placed at f, bisecting Ff, and let the oscillations in this case be 6061 and 606; then the proper position is between Fand f', and so on. Observing always, that if the number of vibrations about C be greater, the slider must move towards C; and if the contrary, it must move towards o. By this means, continually halving the distance last moved, we may make the oscillations about C and O approach within any required degree of exactness; the distance between C and O being then measured, will give the length of a pendulum which makes a known number of oscillations in ten minutes.". I am, Sir, Yours respectfully,

F. R. A.

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A PLAN DESIGNED TO ACCELERATE THE DISCOVERY OF PERPETUAL MOTION.

SIR, SO much has of late been said on this subject, that, in all pro bability, many of your readers are heartily tired of it, and will treat what I am about to advance with the greatest contempt. However, since all that has or can be said will not amount to a proof of its impossibility, perhaps some of those who are in the habit of thinking for themselves may not yet be quite convinced that it is such.

To them I would say, let us for a moment reflect how much the long list of impossibilites has of late years been reduced, and then ask ourselves, if we have not reason to hope for a still further reduction? A few years back, it was impossible to raise our selves more than a few feet from the earth, or to immerse ourselves with safety in the depths of the ocean; and it was equally impossible to traverse its surface to any extent, unless favoured by wind or tide. We can now, however, soar above the clouds, explore the depths of the ocean, and skim over its surface, in spite of wind and tide. And be it for ever remembered, that we owe these and many other advantages to a few persevering individuals, who were, in all probability, stigmatized as chimerical vision aries by those who seem to have an unconquerable propensity to condemn every thing above the level of their own understanding.

If by perpetual motion nothing more is meant than the putting in motion some of the most durable substances with which we are acquainted, in such a manner as to ensure a continuance of that motion as long as those substances will resist the effects of time and friction, I do not despair of seeing it accomplished. Our rapid advances in scientific knowledge, together with the advantages likely to be derived from the "British Invention Company," give us reasonable ground to hope, that the time is not far distant, when even this impossibility must yield to persevering ingenuity. In the present state of public opinion with regard

to its practicability, it would be look-
ed upon as an empty boast, were I to
assert that the discovery is already
made*;
I will therefore only venture
to propose the following plan, which
appears to me likely to expedite so
desirable an object.

Let some well-known public-spirited individuals commence a subscription, and apply the produce to the erection and furnishing of separate work-shops, expressly for the use of those who do not possess the means of putting to the test of experiment any design they may conceive likely to produce the desired effect. Every model made in these shops will belong to the Institution, and should be preserved and properly arranged in a convenient place, appropriated exclusively to their reception. I will not trespass on your valuable pages by specifying the rules, &c., applicable to such an Institution, or by pointing out its advantages, further than to observe, that if it were only to produce a collection of unsuccessful models, accessible to the public, it would be highly beneficial, as it would be the means of preventing any further waste of time and money on what had already proved ineffec tual. But it can scarcely be supposed that it would fail to contribute materially to the progress of science; and as the whole community participate in the advantages derived from science, so every individual (however deficient in original ideas) may, by supporting this Institution, have the gratification of contributing to its advancement. 31 532 of qiut

Such an Institution would be van honour to the country, and though it may not produce the desired effect, it would doubtless be the the means of making many valuable additions to our present stock of mechanical knowledge; and we should not, as was the case with the discovery of the New World, have the mortifica tion of seeing it achieved by means

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*The person who can raise a weight of six ounces to the height of thirteen of four ounces only twelve inches, ought and a half inches, merely by the descent to be allowed to assert that the discovery is made.

SUSPENSION RAILWAY-ELECTRICAL EEL.

of the patronage and support ob-
tained from another nation, after it
had in vain been solicited from us.
And here let me remind your reader,
that it was the outcry set up by the
Antivisionaries, Antichimericals, and
Co., those inveterate foes to every
kind of discovery and improvement,
that deprived us of the honour and
emolument derived from that brilli-
ant discovery, and who still continue
to do more injury to society in one
year, than has ever been done by the
visionaries in a whole century. I
cannot conclude without expressing
my unqualified approbation of the
Mechanics' Magazine. May it ever
continue a vehicle of conflicting opi-
nions, until we arrive at truth on every
subject, is the sincere wish of, Sir,

Your very obedient servant,
PERSEVERANTIA,

Worfield.

SUSPENSION RAILWAY.

SIR,As the subject of Railways has lately been much agitated, and the attention of the public turned to them in no small degree, perhaps it would not be amiss to give place, in your valuable Magazine, to the following abridgment of a newspaper paragaph; it will be only a companion to a late paper on the subject, to which you have given place; and by its insertion you will not only oblige an old correspondent, but perhaps many more, who, having time and inclinaon, would feel a pleasure in taking a trip to see it, the distance not being very great. T. M. B.

1

A line of railway on the suspension principle, invented by Mr. H. R. Palmer, has been constructed for practical use, at Cheshunt, in Hertfordshire, hy Mr. Gibbs, of that place. The line of railway runs from the high road at the lower end of the village, through Mr. Gibbs' land, to the river Lea, and is nearly a mile long. It consists of a single elevated line of surface, supported upon vertical posts of wood, fixed in the ground in a peculiar manner, to render their position secure. These posts are at the distance of about ten feet from

287

each other, varying in height according to the undulation of the ground, so as to keep their upper extremities parallel with the necessary plane. In a cleft on these are laid reverse wedges, on which rests a line of bearers of wood, the upper surface of which, covered with a plate of iron, forms the road for the passage of the wheels. The average height of this road above the ground is from two to three feet. The carriage has two wheels, one placed before the other, and two receptacles for goods, which are suspended, one on each side, the centre of gravity being below the surface of the rail. A number of these carriages are linked together by chains, and a horse is connected with the whole by a towing-rope attached to the foremost machine. The most striking peculiarity of this plan is its extreme simplicity, considering the many obvious advantages it presents beyond the ordinary double rail-road, particularly the great expense it avoids in embankments, culverts, and drains; the trifling space of ground it occupies; the increased effect which can be produced upon it, from its reduced force of resistance; its comparatively small cost; its facilities of loading and unloading, &c. Each carriage contains an oblong box (for passengers or goods), suspended on either side of the rail line, and a quantity of bricks is stowed beneath the seats for ballast; thus one horse drew forty passengers, besides an immense weight of bricks. One carriage, which has been constructed for the purpose of trying the application of the plan to the conveyance of passengers, differs from the others. Its boxes partake partly of the shape of a gig, and partly that of a balloon

car; in each are two cushioned seats

vis-à-vis, with a little dickey behind, the whole carriage being covered with an awning."

ELECTRICAL EEL.

A specimen of the gymnatus electricus has lately been examined by the Parisian suvuns. The greater number were satisfied with a single touch, and consequent shock; but

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