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ON THE STERNBOARD IN STEAMERS; by Commander L. G. Heath, R.N.

It has long been known that if sternway be given to a paddle-wheel steamer, she will, even against her helm and after-sail, pay round off before the wind. An experiment was lately made in H.M.S. Blenheim, which shewed, that the rule holds good also in vessels fitted with the screw. The following reasons are suggested to shew, firstly, why the rudder has less effect with stern than with headway.

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Firstly. To show why the vessel should

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Let A, B, C, D, be the section of a vessel at the waterline; A being the stem, and C the stern-post.. A little consideration will shew that, with sternway, the sides BC D and DC may be considered as two rudders, BC being a port, and DC a starboard one, and that so long as the vessel remains upright, the pressure upon these two rudders, being equal and opposite, counteract one another, and the vessel goes straight astern.

Now, suppose the wind to be a-beam, and the vessel, consequently, to heel over, (say to starboard), the rudder BC will then be raised out of the water a certain quantity, whilst the rudder DC is more immersed by that same quantity; so that the effect upon the vessel is that of a reduced port-helm, accompanied by an increased starboard-helm, and, having sternway, she will slue her stern to port; or in other words, pay off. In short, a similar cause to that which makes a vessel gripe when going-a-head, will make pay off when going-astern; but as the centre of rotation is always in the fore part of the vessel, the steering effect of the lee side is greater with stern than with headway, because it acts on a longer lever.

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Secondly. To shew why the rudder has less effect with stern than with headway.

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Let A, B, C, D, be the horizontal section of a rudder placed at any angle a with the keel.

Let P

pressure of the water on a unit of surface, when the vessel has sternway.

Then by the resolution of forces we have p. sin a. cos a = pressure on each part of BC in a direction at right angles to the keel; and p. cos a. sin a

on each part of AB in the opposite direction.

= pressure

Hence, we see, that at whatever angle the rudder be placed, the turning effect of the back face, exactly counteracts the turning effect of an equal portion of the side face;f so, that, supposing the breadth of a rudder to be six times its thickness, it will lose th of its effect when going astern. This reasoning does not apply

The fact was first pointed out to the public by Mr. Allen, now Master of H.M.S. Blenheim,

For simplicity's sake we have suppose the back of the rudder to be flat and we have taken no account of AB having greater leverage than BC.

to headway, because the fore side of the rudder is shielded by the stern-post.

These explanations taken together, will sufficiently account for the apparent paradox which we have been considering; for the steering effect of the lee quarter, (by which is meant the whole line of the ship's side, from the greatest beam to the stern-post), when going astern, is very much greater than that of the lee bow when going a-head, both from its greater surface, and from its greater leverage; and there is, as our second problem shews us, a smaller counteracting effect on the rudder.

All that has been said above, applies equally to a sailing vessel, as to a steamer; but, the manoeuvre being less frequent, its results have not been so apparent, and have been attributed (erroneously I believe,) rather to the action of the wind on the sails, than to that of the water on the hull.

PURSUIT AND CAPTURE OF THE GENERAL WOOD CONVICTS.
(Concluded from page 553.)

Cambodia.-Via Singapore we have intelligence from Cambodia, or the gamboge country, to the beginning of May. The valuable product which gives name to the country has, for more than thirty years, been the subject of rival claims by Cochin China and Siam. At the south-western extremity of the country is a small island called Pulo Oby, to which place the greater part of the Chinese convicts had escaped who took part in the General Wood catastrophe. To this island and the coast of Cambodia the Hon. Company's steamer Phlegethon was despatched by the senior naval officer (Captain Mac Quhae, H.M.S. Dædalus) at Singapore. The Phlegethon returned in the latter part of May, after a most successful search. From the Straits Times, of May 10th, we abridge the particulars of the Phlegethon's mission:

The Phlegethon, after a pleasant run with fine weather, sighted the island on the eveving of the 11th. At 11h. 30m. P.M. lowered two cutters, the first in charge of the chief officer with boatswain, carpenter, and 14 European and Malay scamen, accompanied by the doctor and purser (volunteers), also the mate of the Celerity, as guide; the other boat, with second officer, midshipman, and gunner, the same number of men, and chief engineer (volunteer,) all armed. Upon leaving the vessel it was soon perceived the task would be no easy one, a strong current running two and a half knots to S. W.; this however, did not dispirit the men, who pulled manfully, and reached the S. E. point of the island about half past 2 A.M. of the 12th. At 4 A.M. their spirits began to lose vigour, fearing the day would break and defeat all efforts; soon finding the current in favour, it was rightly concluded the N.W. point had been rounded and the work must be more easily accomplished, having already gone two-thirds round the island.

Upon opening the bay the sight of two boats at anchor cleared all doubts. Orders were passed for perfect silence; the oars muffled but stoutly pulled. At 5 A.M. the boats grounded some distance from the shore. It being low water the landing was effected with difficulty, many severe cuts were got on the rocks, the rain causing them to afford very uncertain footing. In a short

time the village (which consists of a few mat huts, and a Joss house of the same materials) was surrounded, but in consequence of the over zeal of the guide the sleepers were disturbed before plans were quite matured. There finding the doors guarded, they rushed through the mat work on every side, and thus only eight of the right men were secured, about the same number making their escape into the jungle. One man got dangerously pricked in the lungs with a bayonet, upon his making resistance, but is now recovered. Search was instantly made for articles that would identify them. These were not long wanting: the first being a lady's card case, enclosing a note addressed to Miss Burton, Mrs. Seymour's maiden name; also a lady's work box that had been converted into a receptacle for opium. Government blankets, marked Victoria goal, an English boat's rudder, masts, and sails; these, with the wounded man's confession, confirmed their guilt. Parties were immediately despatched to scour the jungle, and a guard left in the village. The prisoners were secured with their hands tied behind them. Several of them with the false tails they had on, did not stand the test of Jack's steady pull, and in this condition they were sent to the boat. At 8 A.M. finding the steamer not in sight, it was concluded she had also mistaken the situation, and the boat with prisoners was sent to look out. On passing some rocks they observed two China-men issue from a cave, evidently unconscious of what had occurred to their companions. Being hailed and desired to stand they coolly returned to the cave, secured weapons and cloths and took to the jungle. Two or three from the boat immediately landed to give the alarm and one was taken by the look out, but upon making resistance with a knife and bayonet he received a thrust from a boarding pike that passed through his abdomen, causing his death in four hours. In this cave the chronometer was discovered with a large quantity of fish and rice. The steamer now came in sight and anchored in the bay at 8h. 30m. Prisoners, nine in number, including the two wounded, were sent on board: thus ended the first night's enterprise. During the day a second Joss house was discovered on the hills, and one or two large fish and rice depots. It was also ascertained from the inhabitants who had regained confidence, that there was a third Joss house on the opposite side of the island much frequented by the Macao men, and they volunteered to guide.

Two parties were made for the night; one by water and the other through the jungle to meet before daylight; at 2h. a.m. they started, the boat searching the coast, the other the jungle. The Joss house was surrounded at 4h. 30m. but the birds had flown, leaving evident signs of their having recently decamped. Here were discovered, secreted in the long grass, a number of ship's carriages, and bayonets, a large China boat, undergoing repair, and a quantity of salt fish, cooking utensils, &c., all of which were destroyed, the hut and boat burnt; the remainder of their effects they had contrived to carry to the jungle. The only hope now was to regularly hunt them out, no easy task with so few men on such extensive and suitable ground for concealment, the island being one mass of granite, mountainous, and ten or twelve miles in circumference, with numerous caves and almost impenetrable jungle. A ruse de guerre was now attempted. The steamer proceeded to Combodia, leaving a guard secreted in the village, with orders to remain quiet, in hopes they might venture from concealment. On arriving at the entrance of the Camoo river it was considered not prudent to take up the steamer, in consequence of a bar at the entrance, having only one fathom at high water spring tides; consequently the visit of ceremony was performed in a cutter fully mauned, which left the ship with the captain, third officer, and doctor, at 3h. 30m. A.M., on the 22nd, and succeeded by great efforts in reaching the town

at 4h. P.M. the same day, having to pull a distance of not less than fifty miles. The mandarin was prepared for the reception, a boat having been despatched the previous day, intimating the approach of strangers. Invincibles lined the landing, the court, and audience chamber of the palace, with drawn swords and pikes.

After a little delay his Excellency appeared in considerable agitation, doubting our peaceable intentions; but upon ascertaining the mission was merely to request his assistance in capturing murderers, he regained confidence, and ordered the usual luxuries of betel nut, tea, cheroots, &c.; at first he affirmed his inability to comply without reference to the king. This delay, he was made to understand, would not answer the purpose, and his reply would be forwarded to the Queen of England. This produced the desired effect. A consultation was held with his courtiers, and after some controversy it was agreed that a boat with thirty men should proceed to Pulo Oby immediately and remain to secure any convicts not taken; at the same time he would write for permission to send two or three hundred more to search the jungle. He was then requested to assist in procuring live stock, and afford shelter for the night, the men being much fatigued: the audience chamber was then pointed out as the most suitable dormitory; but this was not accepted; a small house near the boat being preferred, which he ordered immediately to be prepared, and the interview ended at 6h .P.M.

The third officer again visited him to urge fulfilment of his promise, reporting the intention of the steamer to await the arrival of his party, at the same time displaying the usual civility on leaving. Upon this occasion he was 'more familiar and polite, making many inquiries, taking down the name of the vessel, officers, &c., and expressed his regret and surprise at the short stay contemplated. Assuring him that the thirty men and stock should leave the next morning, the boat at once returned to the ship, arriving at 9h. P.M. the same evening, and next morning proceeded to the island, having been absent five days, during which time nothing had been seen of the guilty parties. Active measures were again taken; the following day every available person on board was sent on shore, formed into parties in charge of officers, to hunt, and proved their zealous exertions by taking six and viewing four others the first day; the next was not so successful, one only being seen and secured, they having again contrived to conceal themselves. The ship's time-piece was, however, discovered under a tree carefully preserved in a blanket and covered with leaves. This constant search was kept up for five days without success, when a second ruse was tried: the steamer anchoring on the opposite side of the island, and the village being abandoned, leaving directions with the inhabitants, who expressed great alarm at our departure, should any appear, to encourage them, and despatch immediate intelligence. This suc ceeded. The second morning information was brought that some of them had ventured down to get rice; parties were sent quietly through the jungle, and three captured, two making good their escape. In this affray one villian, in making resistance, got his left arm broken. The following day four others were reported to have shown themselves. A party of six, disguised as Cochin Chinese, secretly entered the village, with directions to secure without noise all that approached; but during two days only one appeared; he was, however, persuaded to show some of their hiding places, by which means two others were taken; thus making the number 30, including one killed.

Twelve days having now elapsed since the interview, at Camooe and no signs visible of the promised assistance, the provisions nearly exhausted and none to be procured, four officers and twenty-four of the ship's crew suffering from jungle fever, were circumstances, however unfortunate, that rendered the

return of the steamer imperative. At the same time knowing four or five were left, the inhabitants having decamped to the main land the same day with the steamer, there is little chance of their escaping immediately unless they have money secreted to pay their passage in some of the trading boats, that constantly call for fresh water. This is not likely, none having been found on their persons. They might also be taken away by the piratical junks that infest the island at this season. Two very suspicious craft appeared during the stay of the steamer, but immediately decamped. The villagers report that not less than 70 trading vessels were cut off last year within sight of the island, and that they are obliged to keep all valuables buried, or they would lose everything. Upon carefully comparing evidence, the following account ap pears most to be depended upon. They were about seven days at sea, and arrived at Pulo Oby early in February in two boats. After sailing about the island to reconnoitre, they landed well armed at the village, and immediately took possession. The inhabitants about thirty in number, fled to the jungle; they helped themselves to everything. The largest boat in which it was supposed most of the valuables and treasure were deposited they never left without a strong guard, anchoring in deep water every night; this boat they decked over and otherwise disfigured in the night; with about twelve of their number they left, promising to send a junk for the remainder, the other boat was sunk on the appearance of the Celerity; others have also left by various opportunities. From one of them, Asee, said to be the ringleader, we learn the following result: drowned at Natunas, 15; captured by the natives, 18; gone to China in long boat, 12; to Siam in pukat. 15; gone to Singapore in pukat, 3; gone to Hainan in pukat, 3; gone to Chinchew in pukat, 2; Captured by the Phlegethon, 30; left on Pulo Oby, 5; total Chinese convicts, 93. Two having escaped from the village there is reason to suppose they gave the others information of the danger they were in by exposing themselves. In illustration, of the desperate, reckless, and determined cha racters now brought within the pale of justice, we need only remark that two of the number, whilst on board the steamer, were overheard inciting an attempt to take the vessel; two jumped overboard in the China Sea, one of which got struck by the paddle wheel and perished, the other was saved; a third nearly succeeded in hanging himself.

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CHARTS OF THE COAST OF BRAZIL AT THE ENTRANCE OF THE Rio Grande. THE following account of the loss of the brig Victoria of Liverpool, in consequence of the incorrectness of the charts, has been sent to us for insertion. We trust that the energetic appeal of the writer, who also appears to be the unfortunate owner of the Victoria, will not be made in vain; and that the British Government having already presented to the civilized world a survey of nearly three-fourths of the coast of South America, will not allow her Merchant Shipping to be lost by the deficiency of the remainder, which from the supineness and want of sufficient scientific resources of the Brazilians may be long looked for in vain.

"I have the painful duty to inform you of the total loss of the brig Victoria of Liverpool, from Cadiz to this port, (Rio Grande Brazil) on the night of Saturday last, June 3rd., under the following circumstances.

"The vessel arrived off the bar of this port on Monday May 28th, and the wind being light from the north-east came to anchor in 6 fathoms, the tower bearing due north from the ship. The wind continuing from that point, and

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