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tezuma, about to be delivered; the Panama, in process of fabrication. The Government foundry at Indret, two machines, viz. :—the Cacique, in process of fabrication; the El Dorado, ditto. Four other steam-boats of 220-borse power have been contracted for by MM. Pauwels and Stehelin; they are no* ready for sea, and are named, the Espadon, the Caiman, the Phoque, and the Elan. They are intended to connect the different ports of America.
"One result which has been accomplished, and which is necessary to be observed, is the immense progress which has been made in the construction of machinery. Not very long since the French operative was considered incapable of attaining the same degree of perfection as the Englishman. Some persons even asserted that the organization of a Frenchman would never suffer him to acquire the skill of our neighbours, and that it never would be in our power to compete with them on equal terms. These predictions have been triumphantly refuted. The French operative has demonstrated that this species of natural inferiority, to which it was pretended to condemn him, was an egregious falsehood. All that he required was to be supplied with good tools. Those hare been procured, and our principal foundries are now as well organized as those of England; and France will in future be able to construct her steam machinery as well as she casts the cannon which arms her steam frigates.
"The facts ascertained by the comparison of French and British steamengines afford the most convincing demonstration. At Toulon an experiment was made, in the presence of a commission composed of Engineers and Naval Officers, on the comparative merits of the Labrador, of 450-horse power, whose machinery was built at Cieuzot, and the Asmodee, provided with English engines of the same force. The former was decidedly superior in her speed and in her manner of manoeuvring.
"The instructions given to the ship-builders was to construct the hulls of the vessels in as solid a manner as possible. But it certainly was not foreseen that this solidity should be subject to the proof which the Ulloa had to suffer. A short distance outside the bay of Cherbourg there are some dangerous rocks, which the most practised eye cannot always avoid. On her first sailing from the harbour, the Ulloa, a steam frigate of 450-horse power, ran full on one of those rocks, her speed being at the time from seven to eight knots an hour. Similar p.ccidents nad already taken place, and English vessels had been seen to split in two on the same spot. The Ulloa suffered no damage. After she was carefully examined, she proceeded on her course, and having put on I speed of ten knots an hour she joined the Christophe Colomb.
"On a signal having been given, a third boat of equal force (450-horse power), the Canada, with engines built at Creuzot, sailed from Brest in the direction of Cherbourg. She met the Ulloa manoeuvring, and, confident in her speed, she hastened to accept her challenge; but, she too, was exposed to considerable danger. The pilot, not perceiving the point of the breakwater at Cherbourgh, which was covered by a high tide, steered directly upon it, and passed not only over the breakwater, but struck on a rock inside. The spectators thought she was totally destroyed, but the force with which she s'ruck, and her extreme speed, carried her right into the harbour at the very moment when the guns of the port were announcing the danger.
"The following day the three steam frigates sailed from Cherbourg towards the English coast, having the commissioners and several Engineers on board. The Christophe Colomb and the Canada continued close together during six hour's sailing, at the rate of twelve knots an hour, with a fresh breeze, the wind on the beam. Having reached the Isle of Wight in four hours and a half, they hoisted sail on their return, and their speed was found to be 13 6-10ths hnots nn hour. The Canada returned first to Cherbourg, after a cruise of 13 hours; the Christophe Colomb and the Ulloa were not long in joining her.
"Such results are too conclusive to require any commentary. They exceed all that was anticipated. On their first attempt the French manufacturers reached the level of British perfection, and in some cases surpassed it." We have a right to be proud of our success; we must not'eithcr forget that all the work was completed in the time specified in the contract. The Government Engineers have undertaken the work resolutely; and proved that in France nothing is impossible when we wish it.
"According to official documents, we have 90 steam-boats, either complete or to be finished in a few years. These 90 steam-boats will be propelled by a force of 22,160 horse-power.
"To those must be added 24steam-boats employed by the Post-office representing a force of 3,750 horse-power; which forms a total of 104 ships and 25,900 horse-power."— Times.
On The Mariners' Compass.
Royal Observatory, Greenwich, Nov. 15/h, 1843. Sir.—In your number for the present month, pages 724, and 725, I find the following sentences, in reference to the correction of the disturbance of the compass in iron-built ships:
"The practical directions published by Mr. Airy, although they may be of great practical utility in any iron-built vessel that may navigate the English Channel, or in fact, around the British Isles; yet the plan he has proposed, and the directions he has given are not applicable for distant regions. • • • His method therefore is, to correct the inductive magnetism of the malleable, or cast iron fabric of the vessel by means of permanently magnetic steel bars; that is, to correct or cancel in one hemisphere, by a constant quantity a magnetic agency that may vanish, or from being positive will become negative in the other hemisphere.''
I certainly am surprised that a writer, who appears to possess considerable information on the subject of the mariners' compass, should thus express himself so boldly on a matter on which it is evident that he has not read a word, and does not possess any practical knowledge. These are strong assertions, and I will support them.
In regard to the reading,—there are only two papers published by me which contain the investigations and proofs upon which my process of correction is founded. The first is, a memoir in the Philosophical 7'ransaclions for 1839. The second is, an Appendix to a large work on iron steam-ships, &c, published some lime since by Mr. Weale, which Appendix was almost entirely written by me. From these two papers I inclose verbatim the following extracts, which I request you to print as part of this letter.
Phil. Trans. 1839, p. 196. (The ship to which these remarks apply is the Rainbow.)
"It is quite evident from this table, first, that almost the whole disturbance of the compass is accounted_for by the permanent magnetism."
Page 202.—" On the whole, I conclude that the explanation of the deviations of the compass, by the combined powers of independent magnetism of the ship and induced magnetism produced by terrestrial action, is perfect; and that there is no reason to doubt that by the introduction of antagonist magnets and masses of soft iron, the correction may be made perfect."
Page 210.—" The Ironsides has since sailed to Pernambuco, and her compasses have been correct (as far as general observation goes) through the voyage."
(This vessel has since that time repeatedly made the voyage to South America without alteration of her correcting apparatus, and I am informed, that the compasses so fitted up have always been found correct, in all latitudes.)
Page 211.—" It appears from the investigations above, that the deviations of the compass at four stations in the Rainbow, and at two stations in the Ironsides, are undoubtedly caused by two modifications of magnetic power; namely, the independent magnetism of the ship, which retains ths same magnitude and the same direction relatively to the ship in all positions of the ship: and the induced magnetism, whose force varies in magnitude and direction while the ship's position is changed. It appears also that, in the instances mentioned, the effect of the former force greatly exceeds that of the latter."
Appendix to Weale's Treatise, pages 7 and 8; (the ship alluded to is the Rainbow.)
"Here it is evident that very nearly the whole disturbing force will be represented by the combination of one force directed from the ship's head, and equal to 0-80, and one force directed from the starboard side, and equal to 017; and that the changes in these forces, depending on the position of the ship, are almost insignificant. The inference from this is, that the principal part of the disturbing force is that of permanent magnetism."
Page 11, (in speaking of the Ironsides).—" The forces, then, which are compounded in any position of the ship are: terrestrial magnetism = l'OOO towards the north; permanent magnetism = — 0-386 towards the ship's head; permanent magnetism -\- 0-314 towards the starboard side; induced magnetism — M + P cos. 2 A (p. 181), or — 0-083 + 0028 cos. 2 A towards the north; induced magnetism P sin. 2 A, or 0-028 sin. 2 A towards the east."
To this I may add that the following rule (in the same Appendix, page 15), is intended solely for the correction of the induced magnetism, after that the permanent magnetism has been corrected by permanent magnets.
"Now place the ship with her head exactly north-east or south-west, as shown by the shore-compass; the ship's compasses will, perhaps, be found in error (the error will seldom exceed three degrees). If the needle of one of the ship's compasses point too much to the right, the box of chain must be placed on the starboard or larboard side (it matters not which); if the needle point too much to the left, the box of chain must be placed on the fore or aft side.''
I think I have now sufficiently established my first assertion, viz. that a writer, who states that my method is, " to correct the inductive magnetism of the malleable or cast iron fabric of the vessel by means of permanently magnetic steel bars'", has read nothing upon this subject.
My second assertion is, that this writer has no practical acquaintance with the subject. In proof of this I shall only say that, if be bad once witnessed in observation the apparent caprice in the laws of disturbance of the magnet by an iron-built ship, he would never for a moment have conceived that they could be explained by induced magnetism. I enclose, from the paper in the Philosophical Transactions pages 209 and 210, a statement of the directions of principal disturbance in the Ironsides.
"Another compass in the same ship (a tell-tale, or compass suspended to a beam in the cabin) was observed in regard to deviation only. The observations were made by an incompetent person, and are not worth transcribing. The maximum deviation was greater than that at the binnacle. But this singular circumstance presented itself; that the deviation vanished when the azimuth of the ship's head was 140° and 320° nearly, the maximum + error occurring near azimuth 200°, and the maximum — error near azimuth 80°. At the binnacle compass, the deviation vanished in azimuths 40° and 220° nearly, and its maximum -j- and — errors occurred in azimuths 90° and 340° nearly. Therefore, to make the direction of the ship's independent magnetism at the tell-tale parallel to the magnetic meridian, it was necessary to turn the ship ] 00 degrees further than was necessary to effect the same for the binnacle compass. Or, supposing the head of the ship towards the top of the page, the direction of the magnetic force (as acting on the marked end of the needle)
is / at the binnacle, and \ at the tell-tale. These stations are not, if
I remember right, more than twelve feet apart. In the Rainbow, the directions of the forces on the four compasses were represented by lines as or yS , all included within a small portion of the same quadrant.
To this I may add that I have in my hands a great number of reports on the experiments in different iron-built ships, (some built at Liverpool, some at Glasgow, some in the Thames,) all of which present the same irregularities in the direction of the principal disturbing force. To attribute these to induced magnetism would be ludicrous.
I conclude by expressing my great regret that, in a periodical work of so high a character, and circulated to such an extent among the persons most deeply interested in its contents, an opinion should have been so lightly expressed upon a subject of such importance.
I am, &c,
G. B. Airy,
To the Editor, S/-c. Astronomer Royal.
Lombok: Rice Ports.
It was formerly the custom in Canton to allow ships arriving at that port with rice a large reduction in their harbour charge; which regulation we do not find alluded to in the tariff recently agreed upon between this country and China. Rice, it will be seen upon reference to the list of articles of import into China, is not chargeable with any duty; and, as it may still be found a desirable article of commerce, especially when the crops fail in China—upon which occasions considerable supplies have been heretofore required, and very fair profits have been derived—we think it very possible that the following information respecting the Island of Lombok, and the method of dealing there for rice suitable for the Chinese market, may prove acceptable to
ENLARGED SEMES.—NO. 12.—VOL. FOR 1843. 5 N
our readers; the more so, because we are led to believe that many masters of vessels are desired to proceed to that place for a rice cargo, who have not had an opportunity of acquiring such information beforehand as is necessary to facilitate their operations, and to prevent them from incurring expenses and suffering losses; which older traders, or persons having a previous knowledge of the place and its customs, manage to avoid.
We are advised, that there are six or seven Bandas, agents, Chinese and others, at Ampanam, the two principal men being Banda Baba Java, and Banda Barode. Banda Java is the Queen's Banda, and possesses most influence; but from the Bandas of less consequence, rice is often to be obtained cheaper, although they cannot procure it to quickly. They all usually require advances of cash or goods; and it has been found that in proportion to the advances made, the supply of rice is expedited. Care must however be taken in such negotiations.
As regards quantity, the " koyan" is equal to thirty piculs of 133ilbs. each; but their "dudgeons"', are about two catties and a half short of a picul. It is, therefore, necessary to stipulate, on making a bargain, for full piculs.
The rice is brought in in the morning by women. It is then bagged and weighed, which should always be done in the presence of the purchaser. Two bags are commonly weighed at a time, and two catties on each draft are allowed as tare. A considerable advantage will be gained by taking the women's bags; four such bags (a horse load) weigh three piculs. When the Banda takes these, he weighs them as they are brought in. He then starts the rice, and fills the bags to be weighed and sent off to the purchaser, keeping the overweight which is generally contained in the original bags. This weight is thus lost to the purchaser.
With all " cash" to offer in exchange, rice has been bought at 18,000 cash the koyan, and at less price; but if many ships are, or have been loading, a greater price may be demanded. It is well to bargain that the rice shall be put into the ships' boats; but in this case great attention should be paid to the sailors; who will else cause some trouble by obtaining liquor, absenting themselves, &c.
The Spanish dollar at Lombok ranges in value from 600 to 700 cash, which is the current coin on the island. It has been struck in and sent out from this country of late, and abundantly brought into circulation. 200 of these cash make one "altak," and five " attaks," or 1,000 cash, one " pukeo." The attak is equal to a Java rupee, and is generally called so by the Bandas.
Should a ship requiring rice have no bags of her own, it will cost at least 1,500 cash per " koyan" to supply them, fill, sew-up, and convey them to the boats.
When the payment for rice is to be made part in goods, one-third, perhaps two-thirds, of the value, may be accepted in goods, with the residue in "cash." On all occasions bargains with the Bandas should be made in writing. A few presents are requisite for the Queen and and Rajahs; two or three jars of sweetmeats, bottles of wine, a piece of printed stuff, scissors, &c, are usually provided for this purpose. The "goosties", or princes, are often beggars " of inconsiderable trifles;"