Effect of Damp on Brass Wire.-Sir, A friend of mine lately informed me that be hung up some brass wire in his warehouse, and that part of it which was exposed to damp became to his astonishment, after a short time, as brittle as glass, while that which hung in a dry place was not injured at all. Is there any remedy for wire thus injured? and what is the reason that damp should affect it in so extraordinary a manner? I am, &c.

B. S.

Purifying Oil.-Sir, Having seen in some periodical, (I believe the Literary Gazette,) an account that oil may be purified so as to burn with brilliancy equal to that of gas, by filtering it through charcoal-permit me through your valuable pages to inquire of your correspondents, if any of them can give the particulars of the process. I should also like to know, whether oil that has been kept over last season will answer the purpose? What makes me address these inquiries to you is, that I cannot make my oil (though quite clear) burn in the common way, unless with difficulty; the light being dull and heavy; the wick too continually charring, and therefore often wanting snuffing, otherwise it soon extinguishes. Nor is this the only season I have experienced the same inconvenience. If any of your readers can account for this, or say what I should do to prevent it, they will oblige one who is willing to give as well as receive.

A WEST COUNTRYMAN.

P. S. Since writing the above, I have seen a notice of a lamp called Bright's Shadowless Lamp. Can any of your correspondents favour us with some particulars respecting it? How has it been found to answer in practice? It appears to me to be a very complex thing.

Depriving Oil of Colour. Can oil (linseed oil in particular) be deprived of its colour, by any simple means, without the use of expensive apparatus? Aldersgate, P. Z. August 28, 1829.

Softening Hard Water.-Sir, I have a good well of spring water, but its hardness renders it unfit for many domestic purposes. I should feel greatly obliged if any of your correspondents could point out an easy method of softening it. Westminster.

I am, Sir, yours,

W. S.

Packing Wool-Sir, Being an exten. sive sheep farmer, and finding in common with others of my class, the great injury which the low price of wool inflicts on us, it becomes necessary to endeavour by all means in our power to diminish the expenses attendant on bringing our produce to market. My farm is situated in a very distant part of the island, so much so, that my wool is always sent by sea to Yorkshire for sale. The great volume which the present defective method of packing wool occasions it to occupy, causes the freight to be very heavy; and I wonder very much that no machinery, such as is used for compressing cotton, has been introduced into common use, for the purpose of packing the wool into the same small compass in which the cotton arrives in this country. It may however happen, that there may be something of the sort in existence, which has escaped my notice. I trust in consequence, that you will be kind enough to publish this letter, in the hope that, in reply, I may hear of some machinery which might answer the purpose required. It strikes me that the staple of the wool would not be at all injured, and that a much less freight would be required than when the wool occupies its present extended volume.

I remain, &c.

Peter.

[If our correspondent will consult our 270th Number, he will find in it a description by Mr. Davy of a compressing machine which will probably suit his purpose.-ED]

MINOR CORRESPONDENCE. Wasp or Bee Stings.-Sir, In your Magazine for October last, I perceive your correspondent "P" has given a method of curing the "sting of a wasp or a bee;" also, of preventing infamation where a person has swallowed a wasp: the former by rubbing the part affected with salt and water, and the latter by swallowing salt dissolved in the mouth. I have had several years' experience in the management of bees, and have reason to know that the puncture made by a sting is extremely small, and that in nine times out of ten a person may rub the part a hundred times with salt and water, and not reach the venom. As to his preventing internal inflammation from a sting by swallowing salted saliva, I should be glad to know if he ever tried the experiment, or if he be willing to try it? For stings on my hands and face, I have frequently tried acids and alkalies, and a variety of fluids recommended by Huish and others; and if any of them reached the poison, the pain and swelling immediately subsided, but that was rarely the case. The only method I could depend upon was squeezing the part as soon as possible betwixt the thumb-nail and fore-finger, till I could perceive blood in the puncture; and this I have found a never-tailing cure. have several times been stung in the fleshy part below the eye, and have had it squeezed, as above-mentioned, immediately by another person; and I have never known the operation to fail of success. As to the cure of a sting inwardly, I do not pretend to prescribe: I should have faint hopes of surviving the experiment, though I were drenched copiously with salt. I am, Sir, your obedient servant, Shrewsbury, Nov. 7, 1829.

H.

I

Jackson's Patent Stud for Shoes, &c.-Sir, I ought not to be behind" Mr. Bricklayer" in thanking you for your recommendation of Jackson's studded shoes. Having the Tower-hill district of the Foreign-post under my charge, and of course a great deal of walking, economy in leather is to me au object of the first importance. It is now several months since I had recourse to the studded shoes, and find them to last beyond comparison better than any I ever wore. I can confidently recommend them to my brethren in his Majesty's post-offices, and to pedestrians in general, as most serviceable and desirable. I think they are the best things of the kind yet invented; and I beg leave to add my mite to their praise in your very valuable work, and

I remain your obedient servant, Nov. 16, 1829. L. SMITH. Improvement in Types.-Sir, A thought having struck me that inuch time and expense might be saved, by using a different sort of type to that at present used in printing; I have written to you, in order that if you think the idea worth any thing, you may give it a corner in your valuable publication. My plan is the following: -Instead of each type having one face, let it have two of the same kind one on each side. By this method, a man might compose two sets of types at the same time, and also strike off two copies at the same time; by which means an immense portion of time and trouble might be saved, and thereby much expense.

I am, Sir, your most obedient servant,
E. R. A.
P. P.

Cambridge. ((G. and C.) C.

255

be happy afterwards to offer myself to his notice. I began to make a steam-engine, ten years ago, just large enough for me to carry; but was obliged to give it up for want of means to go on. I have of late made great improvements in the boiler, by lessening its size, increasing the beat, abolishing the smoke, and doing away with the chimney altogether. I believe that a boiler on my plan will produce double the effect of that of Messrs. Braithwaite and Ericsson's. I set out years ago with this text, that it is not the greatest quantity of water that gives the greatest quantity of steam, quite the contrary-it is the greatest quantity of liquid surface, in direct contact with the fire. If the gentleman of Birmingham, or any body else, should adopt my plan, I have no doubt they will find their account in it. I think if one part of this contriv. ance were to be applied to a condensing engine, it would enable it to work always with the same water; but of the certainty of this, experiment must determine. Persous who pay the water companies from 507. to 607. a year for an insufficient supply of injection water (and I know many that do so), might find their account in this also. And if it should answer, the condensing engine might easily be made locomotive, when it would be preferred by thousands to the high pressure one, as was the case with steam-boats when they first came in. With respect to cleaning out the boiler, that is what I have paid great attention to, that it may be done quickly, with certainty, and with ease. I was much pleased with a remark of yours respecting Mr. James's plan for the purpose, (No. 327, p. 197,) and I am sure every one who has had to clean out steam-boilers will be of the same opinion. The playing at marbles I know wont do; perhaps if they were made of steel, and filuted all over and hardened, they might stand a better chance: but the whole will prove a lame thing, I guess.

I am, Sir, yours, &c.
R. M. FRANKLIN.

North place, Wilsted-street, Somers'-town,
Nov. 16, 1829.

Painting on Parchment. A correspondent ("Pit') recommends to such of our readers as may have occasion to use water-colours on parch ment, to go over with alum-water the parts intended to be coloured, in addition to mixing up the colours with it, as recommended by our correspondent "Edward," at p. 330 of our first volume.

MISCELLANEOUS.

Canals of Great Britain.-According to a calculation recently made, there are one hundred and eight canals in Great Britain, extending 2682 miles, formed at an expense of thirty millions sterling.

Self-winding Clock.-The Connecticut Register states, that a person in that state has invented a clock which winds itself up, and keeps correct time, strikes the hour regularly, and will continue to run until worn out, without the application of any power external to itself.

Ripening Wall-Fruit.-A vine-branch had been trained above the window of a house facing the south, according to custom, in certain parts of France. Beneath this branch was a small slate roof, about 3 feet wide, serving to shelter a door. It was remarked, that the grapes on this roof were ripe and black, whilst those on the rest of the branch were yet green. This effect, evidently due to the heat accumulated in the slates from the rays of the sun, has been advantageously applied in assisting the ripening of wall-fruit."M. Banchard-Bull. Univ. D. X.

230.

236

Permanent Ink.-Mr. Murray says, he found ink made of the following ingredients triumphant over the most violent chemical ageeies, and of whose permanence in valuable records there can be no doubt:-

oz. of a solution of nitrate of silver. 1 oz... .... nitrate of iron.

02.

prussiate of ammonia.

oz. of tincture of galls." A portion of finely levigated Indian ink and guin arabic added to these ingredients, is recommended by Mr. Murray. The fluid ounce is to be here understood.

Braconnor's Indelible Ink, or Dye "Twenty parts of Dautzic potash were dissolved in boiling water, and 10 parts of tanned leather parings, in small pieces, with 5 parts of sublimed sulphur, added; the whole was boiled to dryness in an iron vessel; then heated more strongly with continual agitation, but avoiding ignition, until the whole became soft; then a proper quantity of water was gradually added, and the whole filtered through a cloth. In this way a very dark-coloured liquor was procured, which may be preserved for any length of time in wellcorked vessels, constantly excluded from the air: this presents no difficulty to its use, for a pen-full is sufficient to write a couple of quarto pages. It flows much more treely than ordinary ink, does not embarrass the pen with insoluble matter, and resists chemical agents in such a way as to merit the title of indelible ink."-Ann. de Chimie, vol. xl. 221.

Navigation of the Shannon.-We have once or twice incidentally mentioned, with due commendation, a pamphlet by Thomas Steele, Esq. entitled "Practical Suggestions on the General Improvement of the Navigation of the Shannon, between Limerick and the Atlantic." It gives us now much pleasure to learn, that most of these suggestions are in a course of being acted upon, under the sanction and direction of the Chamber of Commerce of Limerick; which has, among other things, recently made application to the Ballast Board of Dublin for the erection of a lighthouse on the Tarbert Rock-one of the improvements most earnestly recommended by Mr. Steele. Limerick, as Mr. S. remarks, "though not a town upon the western coast of Ireland, has the advantage of being deep set on a long inlet towards the heart of the country;" and is thus admirably adapted by its situation to form the seat of an extensive commerce with the West Indies and America, on the one hand, and Dublin, Liverpool, Bristol, Glasgow, &c. on the other; but in consequence of the many dangerous obstructions which exist to the navigation of the Shannon, it has not as yet reaped one-half the benefit which it might derive from its geographical position. We apprehend, however, that Limerick is in this respect but a type of the general condition of Ireland, the capabili ties and resources of which have as yet been only very partially developed. It is with unmixed satisfaction we hail the dawn of a brighter era.

The Holyhead Road and Menai Bridge.-The following eloquent tribute to the merits of these great works appears in the dedication to Mr. Telford, of the work of which we have just quoted, on the navigation of the Shannon, by Thomas Steele, Esq. On the evening when I took my seat as an associate member of the Institution of Civil Engineers, I signed in your presence a declaration that I would always, to the utmost of my power, endeavour to promote the objects for which the society had been founded; and I now, w.thout at all identifying you with my politics, beg permission to dedicate to you the following pages; that at the same time, when I make an humble effort to fulfil my

INTERIM NOTICES.

We presume we are indebted to Civis for & copy of the Chester Advertiser, in which the.. is a letter with that signature on the late Railway Competition, in which the anonymous writer accuses us of making " erroneous statements,"

party spirit," &c. Of the value of Civis's censure, the reader may judge from a slight specimen or two. He says, that he Novelty" (which it is his object in the end to decry) "was con. structed with great attention to appearance and effect, its carriage was light and elegant, and its works being covered in under a copper cap, its motion (as it were without a cause) had the air of magic." Now, so little truth is there in all the latter part of this statement, that the only part covered in under a copper cap" was the steam chamber; and all the other parts of the engine, except the furnace and its flue, were exposed to view. If the reader will have the good. ness to refer to the engraving which accompanies our present Number, he will perceive that "the works' of "The Novelty" were in truth more exposed than those of either of the other engines. Again we are told by Civis, that "another accident which befel this beautiful little engine has, by the Mechanics' Magazine,' been ascribed to the unfavourable state of the railway, while it was actually owing to the bursting of the bellows!!!" A gross and necessarily a wilful misrepresentation.

The "Mechanics' Magazine" never did ascribe any accident which befel "The Novelty" to any such cause, and no "bursting of the bellows" was ever before heard of.

We have already disposed of the Mathematical Question, No. 2, p. 13. of our present Volume, and see no reason for reviving it. The solutions of G. I. Y. and Mr. Russel are both very accurate, and we regret they did not reach us sooner.

Part LXXXII. for November, containing Six Numbers, with the separate Engraving on Stone of "The Rocket, Novelty," and " Sans Pareil," is now ready.

Communications received from Mr. Woollgar -T. V. E.-G. S.-Eliza-Mr. Davy-G. P.Algebraicus.-D. Y. R.-P. T.-J. D.

LONDON: Published for the Proprietor, by M. SALMON, at the Mechanics' Magazine Office, No. 115, Fleet Street; where Communications for the Editor (post paid) are requested to be addressed.

M. SALMON, Printer, Fleet Street.

258

ON THE PROMOTION OF COMBUSTION BY FORCING AIR THROUGH FIRE, AND THE ECONOMICAL APPLICATION OF THE HEAT THUS PRODUCED TO THE GENERATION OF STEAM. BY MR. WILLIAM GILMAN, CIVIL ENGINEER.

In 1826, my attention was directed to the best and most economical method of generating steam, with a view to the improvement of steam navigation, and to other applications where economy and weight are the chief obstacles to the adoption of steam power.

In that year the apparatus exhibit ed by the accompanying drawings was executed, and is now in existence. It was designed to prove prac tically the advantage to be derived from supplying fire with air by means of air-pumps, or other adequate means; and also from various applications of the products of combustion to the production of steam. The drawing, Fig. 1, represents the external appearance, and Fig. 2, a section of the apparatus or generator, which was of great strength on account of the various and sometimes great pressuresfrom 2 to 300lbs. per inch-employed in experimenting.

The generator consists of an internal and external cylinder of cast-iron, each of one inch thick. The internal cylinder, or more properly chamber, containing the fuel, is 18 inches diameter at bottom, whence it tapers upwards to near the surface of the water, where it is reduced more abruptly, and then continued of 8 inches diameter to its termination. The external cylinder is covered with two coats of wrought-iron hoops, each hoop half an inch thick by 2 inches wide, and put on red-hot: thus forming a compact body of metal of 2 inches thick; viz. 1 inch of cast and 1 inch of wrought-iron. The énds or bottom and top of the generator are secured by 12 long bolts, as seen in the drawings, in order to keep the joints perfectly sound. These bolts are made of very tenacious iron, and of a calculated strength to elongate or stretch by a force very much less than would burst the generator. Safety was thus secured at any pressure; for the moment the power of the

steam becomes too great for the strength of the bolt-rods, a small elongation ensues, when the top of the generator is instantly converted into an immense safety-valve-being 2 feet in diameter-and the generator as instantly relieved. The small cylinder H, Fig. 2, is merely for the float B to work in; E, a small pipe to convey steam to the top of the floatchamber to equalise the surfaces of the water in the two chambers; C, a cock to draw off the water when needful; D, the cold water feed-pipe connected to a forcing-pump; A, an airpipe connected with the air-pump, by which the air is introduced below the fire; L, an orifice, of which there are two opposite each other, to which pipes are attached branching from a pipe that passes through the top of the generator, by which the air is conveyed into the chamber above the fire. Neither of these pipes however is shown in the drawing. E is a pipe, of which there are four communicating with the internal chamber above the fire, and dropping nearly to the bottom of the water contained in the space be tween such chamber and the external cylinder. The bottom end of each of these pipes is turned up and fitted with a valve; which valve prevents the water being forced by the pressure of the steam into the fire. The fuel is dropped in from the top, and the opening occasionally closed with a cap a mere temporary experiment however as in constant working it is of course necessary that a regular supply of fuel should be admitted. As the present object is merely to show the principle of action of this generator, it is unnecessary to explain the arrangement by which that object is effected.

In using this generator the method of operating is first to fill the firechamber full of fuel, and when the fuel has acquired a state of intense ignition, the cap of the flue is screwed firmly down; on which the air forced by the pumps through the pipes A and L, and the heated vapours, gases, &c., formed by combustion, acquire density in the firechamber, and when of sufficient power to overcome the pressure of the steam generated in the space between