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will render a service not merely to the Editor, but to the public also, who comply with his invitation to transmit to the publishers any material corrections or additional information.

In a work,' it is remarked in the Preface, embracing such an extreme range and diversity of subjects, as to many of which it is exceedingly difficult, if not quite impossible, to obtain accurate information, no one will be offended, should he detect a few errors. At the same time, we can honestly say, that neither labour nor expense has been spared to render the work worthy of the public confidence and patronage. The Author has been almost incessantly engaged upon it for upwards of three years; and the previous part of his life, may be said to have been spent in preparing himself for the undertaking. He has derived valuable assistance from some distinguished official gentlemen, and from many eminent merchants; and has endeavoured, wherever it was practicable, to build his conclusions upon official documents. But, in very many instances, he has been obliged to adopt less authentic data; and he does not suppose that he has had sagacity enough always to resort to the best authorities, or that, amidst conflicting and contradictory statements, he has uniformly selected those most worthy of being relied upon, or that the inferences he has drawn are always such as the real circumstances of the case would warrant. But he has done his best not to be wanting in these respects. We have had no motive to induce us, in any instance, to conceal or pervert the truth. What we have considered wrong, we have censured freely and openly; but we have not done this without assigning the grounds of our opinion; so that the reader may always judge for himself of its correctness.'

It will be seen from this frank avowal, as might have been anticipated, indeed, from the distinguished talents and well known opinions of the learned Editor, that the work is not the compilation of one who feels himself a tyro, upon whom a neutrality of opinion on subjects demanding the decision of a sound judgement, is imposed by a needful discretion. Professor M'Culloch has not hesitated to intimate his views on the corn trade, the principles of our colonial policy, the West India system, the East India Company, and other topics; and although his readers may not always agree with him, yet, the substantial value and usefulness of the work are not a little enhanced by the general correctness of the commercial principles which it lays down and illustrates. There is no dogmatism, and very little of hypothesis. The Author's data are calculations and facts, which form the staple of the work, the opinions being but incidental. As a specimen of one class of articles, relating as well to natural history as to trade, we take the word Balsam, which will probably supply our readers with some particulars that are new to them.

BALSAM (Ger. Balsam; Du. Balsem; Fr. Baume; It. and Sp. Balsamo; Lat. Balsamum). Balsams are vegetable juices, either liquid, or which spontaneously become concrete, consisting of a substance

of a resinous nature, combined with benzoic acid, or which are capable of affording benzoic acid, by being heated alone, or with water. The liquid balsams are copaiva, opobalsam, balsam of Peru, storax, and tolu ; the concrete are benzoin, dragon's blood, and red or concrete storax.— (Dr. Ure.)

1. Copaiva (Fr. Baume de Copahu; Ger. Kopaiva Balsam; Sp. Copayva), obtained from a tree (Copaifera) growing in South America and the West India Islands. The largest quantity is furnished by the province of Para in Brazil. It is imported in small casks, containing from 1 to 1 cwt. Genuine good copaiva or copaiba balsam has a peculiar but agreeable odour, and a bitterish, hot, nauseous taste. It is clear and transparent; its consistence is that of oil; but when exposed to the action of the air, it becomes solid, dry, and brittle, like resin.(Thomson's Dispensatory.)

2. Opobalsam (Fr. Balsamier de la Mecque; It. Opobalsamo; Lat. Balsamum verum album, Ægyptiacum; Egypt. Balessan), the most precious of all the balsams, commonly called Balm of Gilead. It is the produce of a tree (Amyris Gileadensis), indigenous to Arabia and Abyssinia, and transplanted at an early period to Judea. It is obtained by cutting the bark with an axe at the time that the juice is in the strongest circulation. The true balsam is of a pale yellowish colour, clear and transparent, about the consistence of Venice turpentine, of a strong, penetrating, agreeable, aromatic smell, and a slightly bitterish pungent taste. By age it becomes yellower, browner, and thicker, losing by degrees, like volatile oils, some of its finer and more subtile parts. It is rarely if ever brought genuine into this country; dried Canada balsam being generally substituted for it. It was in high repute among the ancients; but it is now principally used as a cosmetic by the Turkish ladies.-(Drs. Ure and Thomson.)

The Canada balsam, now referred to, is merely fine turpentine. It is the produce of the Pinus Balsamea, and is imported in casks, each containing about 1 cwt. It has a strong, but not a disagreeable odour, and a bitterish taste; is transparent, whitish, and has the consistence of copaiva balsam.

3. Balsam of Peru (Fr. Baume de Peru; Ger. Peruvianischer Balsam; Sp. Balsamo de Quinquina; Lat. Balsamum Peruvianum), the produce of a tree (Myroxylon Peruiferum) growing in the warmest parts of South America. The balsam procured by incisions made in the tree is called white liquid balsam; that which is found in the shops is obtained by boiling the twigs in water: it is imported in jars, each containing from 20 to 40 lbs. weight. It has a fragrant aromatic odour, much resembling that of benzoin, with a warm bitterish taste. viscid, of a deep reddish brown colour, and of the consistence of honey. (Thomson's Dispensatory.)

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4. Storax (Fr. Storax; Ger. Stryaxbroom; It. Storace; Sp. Azumbar; Lat. Styrax; Arab. Usteruk), the produce of a tree (Styrax officinale) growing in the south of Europe and the Levant. Only two kinds are found in the shops: storax in tears, which is pure; and storax in the lump, or red storax, which is mixed with saw-dust and other impurities. Both kinds are brought from the Levant in chests and boxes. Storax has a fragrant odour, and a pleasant, sub-acidulous,

slightly pungent, and aromatic taste; it is of a reddish brown colour, and brittle. (Thomson's Dispensatory.)

5. Tolu, Balsam of (Fr. Baume de Tolu; Ger. Tolutanischer Balsam; Sp. Balsamo de Tolu). The tree which yields this balsam is the same as that which yields the balsam of Peru; it being merely the white balsam of Peru, hardened by exposure to the air.

6. Benzoin, or Benjamin (Fr. Benzoin; Ger. Benzoe; Sp. Bengui; It. Belzuino; Lat. Benzoinum; Arab. Liban; Hind. Luban ; Jav. Menian, Malay, Caminyan), is an article of much greater commercial importance than any of those balsams previously mentioned. It is obtained from a tree (Styrax Benzoin) growing in Sumatra and Borneo. It has a very agreeable fragrant odour, but hardly any taste. It is imported in large masses packed in chests and casks. It should be chosen full of clear, light-coloured, and white spots, having the appearance of white marble when broken: it is rarely, however, to be met with in so pure a state, but the nearer the approach to it the better. The worst sort is blackish, and full of impurities.—(Milburn's Orient. Com.)

Mr. Crawfurd has given the following interesting and authentic details with respect to this article:-" Benzoin, or frankincense, called in commercial language Benjamin, is a more general article of commerce than camphor, though its production be confined to the same islands. Benzoin is divided in commerce, like camphor, into three sorts, (head, belly, foot,) according to quality, the comparative value of which may be expressed by the figures 105, 45, 18. Benzoin is valued in proportion to its whiteness, semi-transparency, and freedom from adventitious matters. According to its purity, the first sort may be bought at the emporia to which it is brought, at from 50 to 100 dollars per picul (1333 lbs.); the second from 25 to 45 dollars; and the worst from 8 to 20 dollars. According to Linschoten, benzoin, in his time, cost, in the market of Sunda Calapa or Jacatra, from 1915 to 25-40% Spanish dollars the picul. By Niebuhr's account, the worst benzoin of the Indian islands is more esteemed by the Arabs than their own best olibanum, or frankincense. In the London market, the best benzoin is fourteen times more valuable than olibanum, and even the worst 2 times more valuable. Benzoin usually sells in England at 10s. per pound. The quantity generally imported into England, in the time of the monopoly, was 312 cwts. The principal use of this commodity is as incense, and is equally in request in the religious ceremonies of Catholics, Mohammedans, Hindus, and Chinese. It is also used as a luxury by the great in fumigations in their houses; and the Japanese chiefs are fond of smoking it with tobacco. Its general use among nations in such various states of civilisation, and the steady demand for it in all ages, declare that it is one of those commodities, the taste for which is inherent in our nature, and not the result of a particular caprice with any individual people, as in the case of Malay camphor with the Chinese."-(Indian Archipelago, III. p. 418.)

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7. Dragon's Blood (Fr. Sang-Dragon; Lat. Sanguis Draconis; Arab. Damulakhwain; Hind. Heraduky), the produce of a large species of rattan (Calamus Draco) growing on the north and north-east coast of Sumatra, and in some parts of Borneo. It is largely exported

to China, and also to India and Europe. It is either in oval drops, wrapped up in flag-leaves, or in large and generally more impure masses, composed of smaller tears. It is externally and internally of a deep dusky red colour, and when powdered, it should become of a bright crimson; if it be black, it is worth little. When broken and held up against a strong light, it is somewhat transparent: it has little or no smell or taste; what it has of the latter is resinous and astringent. Dragon's blood in drops is much preferable to that in cakes; the latter being more friable, and less compact, resinous, and pure than the former. Being a very costly article, it is very apt to be adulterated. Most of its alloys dissolve like gums in water, or crackle in the fire without proving inflammable; whereas the genuine dragon's blood readily melts and catches flame, and is scarcely acted upon by watery liquors. Its price at Bajarmassin in Borneo, where large quantities are manufactured, is, according to quality, from 50 to 70 Spanish dollars per picul, or at an average 117. 6s. 94d. per cwt. Its price in the London market is usually about 30l. per cwt.—(Milburn's Orient. Com. Crawfurd's East. Archip.)

The net duty on balsams imported into Great Britain in 1828 amounted to 5,543l. 7s. 8d.' pp. 57, 8.

As an article of a different character, uniting trade and mechanics, we take the word Rail-road.

‹ RAIL-ROAD, TRAM OR WAGON ROAD, a species of road having tracks or ways formed of iron, stone, or other solid material, on which the wheels of the carriages passing along it run. The object in constructing such roads is, by diminishing the friction, to make a less amount of power adequate either to impel a carriage with a greater velocity, or to urge forward a greater load.

Construction of Rail-roads.-The friction on a perfectly level railroad, properly constructed, is estimated to amount to from th to 4th only of the friction on an ordinary level road; so that, supposing the same force to be applied in both cases, it would move a weight from 10 to 7 times as great on the former as on the latter. But if there be a very moderate ascent, such as 1 foot in 50, which in an ordinary road would hardly be perceived, a great increase of power on the rail-road is required to overcome the resistance that is thus occasioned. The reason is, that the ordinary load on a level rail-road is about seven times as great as on a common turnpike road; so that when the force of gravity is brought into operation by an ascending plane, its opposing power, being proportioned to the load, is seven times as great as on a common road. Hence the vast importance of having rail-roads either level, or as nearly so as possible.

It is also of great importance that rail-roads should be straight, or, at least, free from any abrupt curves. Carriages being kept on the road by flanges on the wheels, it is obvious, that where the curves are quick, the friction on the sides of the rails, and consequent retardation, must be very great. In the Manchester and Liverpool rail-road, the curves form segments of a circle which, if extended, would embrace a circumference of 15 miles.

VOL. VIII.-N.S.

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Speed of Carriages on Rail-roads, &c.-The effect of rail-roads in diminishing friction is familiar to every one; and they have long been used in various places of this and other countries, particularly in the vicinity of mines, for facilitating the transport of heavy loads. But it is only since the application of locomotive engines as a moving power, that they have begun to attract the public attention, and to be regarded as of the highest national importance. These engines were first brought into use on the Darlington and Stockton rail-road, opened on the 27th of December, 1825. But the rail-road between Liverpool and Manchester is by far the greatest undertaking of this sort that has hitherto been completed. This splendid work, which is executed in the most approved manner, cost between 800,000l. and 900,0007.; and as far as speed is concerned, has completely verified, and, indeed, far surpassed, the most sanguine anticipations. The road has the advantage of being nearly level; for, with the exception of a short space at Rainhill, where it is inclined at the rate of 1 foot in 96, there is no greater inclination than in the ratio of 1 foot in 880. The length of the rail-road is 31 miles; and it is usual to perform this journey in handsome carriages attached to the locomotive engines, in an hour and a half, and sometimes less! So wonderful a result has gone far to strike space and time out of the calculations of the traveller: it has brought, in so far, at least, as respects the facility of passing from the one to the other, Liverpool as near to Manchester as the western part of London is to the eastern part!

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The extraordinary speed of carriages on rail-roads depends on the fact, that the friction, which on a perfectly level rail-road is the only resistance to be overcome, is the same for all velocities; so that, abstracting from the resistance of the air, which is so trifling as not to require to be taken into account, we have merely, in order to double or treble the velocity, to double or treble the power. But in vessels at sea, or in canals, which have to make their way through a comparatively dense medium, the resistance to be overcome increases as the square of the velocity; so that to double the speed, the power must be multiplied by 4, and to treble it, it must be multiplied by 9, and so on. Comparative Advantages of Rail-roads and Canals.-Astonishing, however, as are the results of the performances on the Manchester and Liverpool rail-road, we doubt much whether there be many more situations in the kingdom where it would be prudent to establish one. That carriages with passengers may be safely impelled along a perfectly level rail-road at a speed of 20 or 30 miles an hour, is a fact that is now proved experimentally; but before deciding as to the expediency of opening such a mode of communication between any two places, it is necessary to look carefully into the expense attending the formation of a rail-road with a suitable establishment of carriages, at the expense of keeping it and them in repair, and at the probable returns. The outlay, judging from what has taken place between Liverpool and Manchester, is quite enormous; the wear and tear of the engines, which is great under all circumstances, is increased in an extraordinary degree with every considerable increase of speed. We do not, therefore, consider the success that has hitherto attended the Liverpool and Manchester rail-road as at all warranting the construction

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