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losing the elastic form, and may be partly an effect of the electricity in making its escape from the cloud. The thunder and lightning which sometimes attend the condensation of large volumes of steam emitted by volcanoes, are favourable to this theory; as are likewise the noise and lightning of the water-spout, if not some parts of the Northern Lights.

Remarks on Captain Pakenham's Temporary Rudder, and

explanatory of an Alteration proposed. By Commander

John PEARSE, R. N. Having twice witnessed the application of that most useful invention, it has frequently occurred to me that it may be made much more effective, and the labour and time in making reduced, without lumbering a ship with any additional materials, except something to secure the heel of it in place of the spare lower cap.

The rudder being such an essential part, and requiring to be replaced as expeditiously as possible, in the event of its being damaged or lost by a ship getting on shore, or, which sometimes happens, at sea; and, on such occasions, ships having to depend on their own resources, particularly on long voyages, has induced me to offer the following remarks on it, and an explanation of an alteration I propose.

The top-rope sheave holes being necessarily cut in the spare topmasts, for the expedition of shifting in case of emergency, the mast is so much weakened by it where the most strength is required, when applied as the main piece of a temporary rudder, and twists so much when the ship carries a weather helm, that it frequently becomes necessary to ease it as much as possible by furling the after sails. This defect may be remedied by supplying one piece of pine timber of the length, and in lieu of the two yard-arm pieces which are given to all king's ships as sea store.

Figure 1st, in the accompanying wood-cut, represents the temporary rudder agreeable to Captain Pakenham's plan. By which it will appear evident, that the rudder is considerably weakened by the sheave hole where the greatest strength is required. The diameter of the sheave hole A is one

sixth of the diameter of the mast, and which, from the sheavehole being through its centre, is reduced in strength and substance full one-fifth..

It also requires considerable time and labour to convert the spare lower cap, to adapt it to the purpose of securing the heel. The wood of the aft-part, at B. fig. 2. requiring to be cut out

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to admit of the cap fitting on to the stern-post, and conșequently, the brace bolts at C. to be driven out, or cut through with a hack saw; the brace bolts at the fore-part also require to be cut, to admit of the corners being rounded off. The bulk of the cap must also contribute to the tendency of the rudder to lift, by the sending motion of the ship in a sea, except it is fitted close under one of the braces, which is not practicable if the pintles are broken and remain in, as is generally the case when a rudder is lost.

From the buoyancy of the materials the rudder is composed of, it is also necessary to append iron ballast to the heel, to sink and facilitate the hanging of it; all of which would be greatly remedied by a cast composition cap, as described in fig. 3. being supplied for the purpose. As its weight would obviate the necessity of appending ballast to the heel, its small bulk would add but little to the tendency of the rudder to lift in a sea; and the time and labour of converting the spare lower cap saved.

The greatest difficulty in hanging it, particularly if there is any motion, is, to conduct the cap to its place. From the position of the eye bolts D, in the spare lower cap, the hawsers which are fastened to them, and which secure it to the stern-post, can be no guide to lead it to its place, consequently it is necessary to have guys to assist it; and which would be remedied by the composition cap 1 propose, as the hawsers being fastened to the eyes EE would lead it immediately to its place, and obviate the necessity of having so many ropes, which are liable to confuse and get foul of each other. · Line-of-battle ships are allowed only two spare pintles as I have represented in fig. 1. I should propose these being supplied, as it would make the rudder much more secure; and the third brace down, not being much below the surface of the water, can easily be cleared of the pintle if broken and remain

ing in,

In an eighteen gun-brig, which I was serving as first lieutenant, the temporary rudder was put together and hung in twelve hours. By the alteration I propose, and the superior resources of a large ship, it could no doubt be done in much less time; and it is a much more expeditious means of rendering a ship effective than repairing the pintles, when they are broke and the rudder saved. Accidents, too, may occur, when and where it is absolutely necessary a rudder should be hung before they can be repaired, which, with good smiths, on board a ship, would require several days.

Figure 4th represents the rudder composed of the materials I propose ; by which will be seen the difference in bulk of the composition cap and the spare lower cap as represented in fig. 1. It will also be seen, that the alteration I propose strengthens the rudder below, as the space required for its working round the end of the cap in fig. 1, is much larger than in fig. 4.; it also hangs closer to the stern post below.

It is not only king's ships that should be supplied with the means of putting together as effective a temporary rudder as possible, but also Indiamen, and all merchant-ships going long voyages; and having such, I have no doubt two good carpenters in a merchant-ship, would put one together in twenty-four hours.

Plymouth, 14th Feb. 1829.

Analysis of the Mineral Water of Bath.

[Communicated by Mr. A. Walcker.] Since the latest experiments which the springs of this celebrated watering-place have been submitted to by Dr. Scudamore, our attention has been directed, by the masterly analysis of the Carlsbad and some other Bohemian springs by Berzelius, to look out, in the analysis of mineral waters, for several ingredients which were previously not supposed to exist in them. From this consideration, I was induced to subject the Bath water to a new analysis ; and, although I wished to spare the reader the perusal of its dull details, yet I think it necessary to state briefly the processes which I have followed, in order to enable him to judge what reliance may be placed in their correctness.

I am indebted for the supply of the mineral water to Mr. R. F. George, M.C.S. of Bath, who was kind enough to have it bottled, with due precautions, under his own inspection, from the pump

in the pump-room. The mineral water, when I received it, was very slightly turbid; the suspended precipitate appeared to consist chiefly of silica, an excess of muriatic acid and application of heat having but very little effect in restoring its transparency. The specific gravity of the water at 60° F. was found to be 1.00202.

In the filtered mineral water, nitrate of silver indicated the presence of chlorine. • When evaporated to go of its original weight, and strained off from the precipitate formed, solution of starch and nitrous acid gave no indication of iodine ; nor was bromine to be detected by the addition of chlorine ; nor nitric acid by boiling it with a gold leaf, and a due quantity of sulphuric acid.

The residue of the water (the carbonates of which had been converted into acetates, in order to prevent the fluosilic acid, if present, from being carried off too rapidly along with the carbonic acid gas) gave no indication of fluoric or fluo-silicic acid, when treated with sulphuric acid in a platinum vessel, covered with a wet watch-glass.

Ebullition proved the presence of carbonic acid in the mineral water, by the precipitation of carbonate of lime,

Muriate of barytes indicated sulphuric acid.

A portion of the mineral water, to which an excess of carbonate of soda was added, was evaporated to dryness, and the residue dissolved in water. A part of this solution was supersaturated with nitric acid, and precipitated with an excess of nitrate of silver. The liquid, separated from the chloride of silver, gave no indication of phosphoric acid, by being duly neutralized with ammonia ; nor could any indication of phosphoric acid be obtained, when the solution was precipitated with muriate of barytes, and the fluid strained off from the sulphate of barytes was mixed, after ebullition, with an excess of ammonia. The earthy carbonates obtained in this experiment left silica, when dissolved in muriatic acid. The muriatic solution indicated iron, by the addition of ferro-prussiate of potash. Sulphuretted hydrogen produced in the acid solution a slight precipitate of sulphuret of lead.* Ammonia produced a

* In a solution which contains at the same time oxide of lead and peroxide of iron, sulphuretted hydrogen does not produce a precipitate of lead, till the peroxide of iron present is reduced to the state of protoxide; and sulphuret of lead, already formed, can be re-dissolved by the addition of a solution of per-chloride of iron. The sulphuret of lead, whenever it is precipitated from a solution which contained at the same time a peroxide salt of iron, appears of a lighter colour, (from the ad.

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