content of the tree to be near, and most commonly above, one-fifth part less than the true content. But, for the maintaining of this ill custom, they plead the overplus measure may be well allowed, because the chips cut off are of little value, and will not near countervail the labour of bringing the timber to a square, to which form it inust be brought before it be fit for use. To this I answer, that although the chips in small timber sticks be but of small value, yet, in great trees,

45

error prevail against truth, nor ignorance convince reason supported by art, upon demonstration."

Before I close this subject, I beg leave to recommend to the notice of your readers the rule for measuring round timber first proposed by Dr. Hutton; it is much nearly as easy in practice. It is this:more correct than the common one, and girt, or circumference, by twice the Multiply the square of one-fifth of the length, and the product will be the soli

of hewing is not lost, and only the chips allowed; but, notwithstanding, I do not say that timber standing ought to be measured falsely, but truly, and if any allowance be to be made, let it be in the price, and not in the quantity; and, as the quantity will be 1-5th part more than in reality it is, so a fifth part might rather be abated in the price. Besides this, if timber be thus measured, and bought when it is round, I say that a tree, when it is hewed, and brought to such a square as timber is usually brought to, and measured as it there is hewed, that timber stick shall then hold out more measure than when it was bought round. Divers other errors in the mensuration of solid bodies have crept in for the lack of art, and the ignorant being possessed thereof do plead prescription and custom, whereas custom cannot establish a law upon a bad foundation and false ground, neither can

demonstrated as follows :

Let g the girt, or circumference,

and L the length, thus :

g2 L 12.5'

2

× 2 L

=

the content of the tree according to the above rule; and the true content, measuring it as a cylinder, is, 1 g2 × XL = g2 L x2 the 2×3.1416 ; 12.5664 difference between which and the former expression is not worth notice.

as not to perceive that either of them has made any improvement at all. I am employed every day in the year, Sunday and holiday excepted, at bell-hanging, and I never met a situation, either bevel or circular, internal or external, but what the common bevel crank was perfectly adequate to. The only improvement that I could ever make, was to file off one of the eyes, when working round an obtuse angle, and putting both wires in the other.

Fig. 1 represents the bevel crank.
Fig. 2, the circular wall and bevels.
Fig. 3, the same when the bell is drawn.

There is another difficulty in bellhanging which I consider a real one, namely, that of boring perfectly ho

rizontal for door-pulls. Now, Sir, if either of your bell-hanging Correspondents would just oblige us with an improved method of the above, or an infallible method of detecting a crooked bore, it would be doing a service, for which they should have my warmest thanks, and more than mine, I well know; for only to a bell-hanger is known the grief of mind felt, when, after entering, as he thinks, perfectly horizontally, and boring two feet, or two feet six inches, he finds himself an inch, or an inch and a half, out of course. Boring an oak-case, too, is no treat. I am, Sir,

Your obedient servant,

A. S.

height in the pillar, and thus produces a constant supply from within, in the same way that the common lamp is supplied from without. The variation of the altitude of the oil in the pillar is equal to the depth in the cylinder; hence, if the breadth of the cylinder is great, the variation of the altitude of the oil will be small. The glass placed on the capital of the pillar may be spherical, or of any other shape, and will cast no shade. I am, Sir, Yours respectfully,

F. O. M.

DUTY ON IRON, COPPER, ZINC, ETC.

An intelligent Correspondent, in our 82nd Number, complained of the extravagantly high price which iron has recently attained, in consequence of the inadequacy of our home supply of that article, and urged the policy of permitting a free import of foreign iron, in order to bring the price of this necessary commodity to its proper level. We have since observed, with much pleasure, that a large reduction of the duty, not only on foreign iron, but on foreign metals generally, is one of the many beneficial measures which his Majesty's Ministers (the greatest radical reformers we know of) have brought into Parliament for the promotion of the manufactures and commerce of the country. Mr. Huskisson, in proposing this reduction, mentioned some very striking facts in support of it.

"He knew," he said, "that there were at the present moment extensive orders in Sheffield and Birminghamsome of them from North America, others from several parts of the South American provinces-which could not be executed, because they were sent with a limitation of price; and he also knew that very many individuals were now employed in making models of the kind of articles wanted, which were to be sent off to Germany, where the orders could be executed at a very reduced price.--(Hear, hear.)-Was not this, he would ask, quite enough to show the great importance of having those duties reduced? Was it not an injurious monopoly, thus to exclude a foreign supply, and confine the market to the produce of the country, which was really not sufficient to supply the general demand. It was of the utmost advantage to this country to have, in the manufacture of many articles, a mixture of foreign iron, particu

47

larly Swedish, which was superior to the irou smelted with coal. The want of a sufficient supply of that iron (in consequence of the high duties) had caused a deterioration in the quality of several important articles of our iron manufacture, and would produce a consequent diminution of the demand. In the manufacture of iron cables, for instancez which had of late come into very general use in our ships, a mixture of Swedish iron was considered of great advantage, and those cables in which it was used were considered the best. Here, then, a most important benefit to our naval interests might be counteracted or prevented by continuing the present high duties; the reduction of duty on this article was on every account advisable. The next article upon which he intended to effect a reduction was copper. The state in which the English manufacturer was placed by the high duty on iron was not more injurious than that in which he was placed by the high duty on copper. The duty on the importation of copper was at present 547. per ton. Now, if we attempted to maintain the duty at this high rate, and to keep up the price of our copper manufactures accordingly, it was evident that we must ultimately be driven from the market by our incompeteucy to contend with the foreign manufacturer; whereas, if we lowered the duty, and so enabled our manufacturer to furnish a superior article at a lower price, we should soon become the ma

nufacturers of it for the whole world.

The consumption of copper amounted at present, in each year, to 10,000 tons, of of which 4000 or 5000 were used at home, whilst the remainder were exported to the foreign market. Now, the owners of copper-mines must see, that if by the high price at which the manufacturer bought copper, he should lose his hold upon the foreign market, they must be injured by the effects of their own monopoly. The supply of copper would be diminished more than one-half, and they would therefore lose more by the continuance of the present duties than they would run the risk of losing by the repeal of them. Besides, they ought to recollect, that in this article a new field of supply had recently been opened on the world. Copper was plentiful in many of the States of South America; and if our policy in imposing on it high and prohibítory duties had not prevented it from coming into this country, we should have had a much greater manufacture of copper than we had at present. By prohibiting the importation of copper, other countries had been compelled to undertake the manufacture of it themselves; they had discovered means of rolling and preparing it, and were ac tually employing our machinery to do that which we should have had an op

portunity of doing ourselves, had it not been for our impolitic restrictions. A supply of copper was poured into Europe from Chili: of that supply we might have been the masters, if we had not placed on the article such an enormous duty as incapacitated other countries from purchasing it at our hands. A difficulty was always found in reconciling the conflicting interests of the manufac turer and the consumer of an article. He was, however, of opinion, that he should do good to both in reducing the duty on copper from 547. to 277. per ton. That reduction would relieve the evil which pressed at present on the coppermanufacturer of the country, and would be productive of consequences which, he trusted, would enable him, in another session, to propose to the Committee even a still larger reduction. There was another article in which he thought that he might safely propose an alteration of duties. It was the article of spelter, a metal better known by the name of zinc. The duty on the importation of it into this country was 281. per tou. The selling price of it at Hamburgh was 307. per tou, whilst in England it was from 407. to 50%. per ton. This article formed a third part of the composition of brass; so that with this duty of 281. per ton on the zinc, and a duty of 547. per ton on the copper which went to its formation, how could they suppose that the English manufacturer could support himself against the competition of the foreign manufacturer? The great occupation of our manufacturers at present was, to furnish patterns for the foreign manufacturers, which they were unable to furnish for themselves. He proposed to reduce the duty on this article full onehalf. He believed that the reduction ought to go still further, but he would not press it at present, in consequence of some individuals having capital engaged in the mines of this country,which, however, could not in any respect compete with those of Silesia."

OPENING OYSTERS.

SIR, Observing, in the Mechanics' Magazine, No. 83, page 418, a quick method of Opening Oysters, which, in some respects, is objectionable, as I have made use of it myself. The objection is, it always pulverizes some portion of the shell, which the knife is likely to carry in; and I have found a large portion of the thick lower shell to break off, and spoil the oyster, after every care. I have adopted another method, where a person is in possession of the mechanical power, thus described:-Take hold of an oyster, placing the thumb on the upper shell and

two or three fingers to the lower shell; place the sides of the shells between the cheeks of a strong fixed vice: the screw of the vice acts so regularly that the upper shell is seen to rise sufficiently to get the well-sharpened edge of a dessert knife in, to cut the heart of the oyster from the lower shell: take the oyster out of the vice, and the upper shell is easily forced off. I think a man, with some adroitness, can open a large dishful, to set upon a supper table, in half an hour. I have observed some persons prefer them off the shell, to eating them off a plate, with vinegar and pepper; and I have seen an oyster taken up with a fork, with a beard hanging down like a Jew, the oyster half cut in two, with streaks of black mud on its whiteness. Though this may be called a lazy, slow way of opening them, yet where is the man who objects to a well-cooked dinner or a clean-opened oyster, even if he waited a short time? As I live only a few miles from the eastern coast of Essex, where we have the best, and eat plenty, I would suggest a method of preventing oysters having black streaks. Put a peck of oysters into a large round flat tub, or, what is better, a stone trough, under a pump; plug the stone up; pump six or eight inches of water; make a servant, with a birch broom, brush them for four or five minutes with some force; unplug the stone, and let the dirty water out. With eight or ten strokes of the pump wash them clean, and the shells will not soil a lady's fingers. To keep them-put them, by layers, into a large flat oval yellow dish, sprinkling salt over each layer except the last, then covering them two inches with water, sprinkling over the water a handful of salt, and, at the same time, one or two handsful of oatmeal; set them in a cold cellar, changing the water every three days. This is of no use in London, because, perhaps, at the next door lives an oyster-merchant. But what is more agreeable, in the country, when a hungry friend, from a journey, drops in at nine o'clock, than to set before him a dish of fine oysters? It whets his appetite, and becomes an apology for an empty larder. I am, Sir, yours,

April, 1825.

MONTIS.

**Notices to numerous Correspondents in our next.

Communications (post paid) to be addressed to the Editor, at the Publishers', KNIGHT and LACEY, 55, Paternoster-row, London. Printed by B. BENSLEY, Bolt-court, Fleet-street.