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PROMOTION OF COMBUSTION BY FORCED AIR.

therefrom to be of an elasticity inferior to that of the atmosphere, yet with the assistance of the exhaustingapparatus it may be rendered applicable to most of the above-described purposes.

The value of the heat obtained from the steam after passing through the engine, and the elastic fluid at the termination of the generator or boilerflue, must depend of course entirely on the necessities of the establishment in which the engine is erected; but without taking this at all into account, I think it will be manifest that the several plans are capable of generating power with the smallest quantity of fuel possible, and possess the pre-eminent quality of destroying the smoke and rendering a chimney totally unnecessary. The mode adopt

ed in the last modification of obtaining a draught by an exhausting-apparatus, is particularly adapted to the purpose of destroying the smoke of existing furnaces where there is an engine by which the apparatus can be kept in action; and as I believe it to be entirely free from the objections to which most of the plans hitherto proposed for effecting so desirable anˇobject is liable, it merits the particular attention of the proprietors of the numerous establishments, especially in London and other large towns, whose immense volumes of smoke render them at present a nuisance to the whole neighbourhood in which they are situated.

Yours, &c.

WILLIAM GILMAN.

7, Ratcliffe-highway.

P. S.-I perceive I have omitted to state, that it is not absolutely necessary that the exhausting apparatus should be placed immediately over the surface of the water, as described in the last modification, as such apparatus may be fixed under the enginebeam, and worked thereby, or by a crank in any other convenient situation, and connected to the chamber above the water-surface by a suctionpipe: also, that if the heated water, in which either of the flues terminates, is required for any purpose for which it is not fitted by reason of its impurity through its retention of the carbonacious matter, such impurity may

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be in a great measure remedied, by causing the vapour and gases rising from its surface to flow into a second vessel, in like manner to that of the first; which water may be used for feeding the boiler, and many other purposes. The loss of heat, by using the second vessel, will be insignifi

cant.

[We mentioned generally last week the obvious similarity between Mr. Gilman's plans and those of Messrs. Braithwaite and Ericsson. This similarity is not confined to the plan of gaining heat by means of forced air, but extends also to the mode of producing a draught or current of air by means of an air-exhausting apparatus at the end of the furnace-flue. In the

specification of Messrs. Braithwaite and Ericsson's patent, it is stated that their invention" consists in generating steam in a boiler, wherein the capacity of the flue is too small to allow a sufficient quantity of heated air to pass through in a given time by the mere agency of what is commonly called atmospheric draught, and to which flue therefore we attach either an air-forcing apparatus at the furnace end, (as in "The Novelty,") or an airexhausting apparatus at the other end of the flue, in order by these mechanical means to compel the required quantity of heated air to pass through the flue in a given time." With whom the merit of priority lies we do not presume to say, and have not, in truth, the means before us of determining; for though Messrs. Braithwaite and Ericsson's patent is, we believe, of a more recent date than the invention described by Mr. Gilman, it is not always from the date of a patent that the date of the discovery included in it, is to be inferred. Messrs. Braithwaite and Ericsson will probably favour us with some farther information on the subject.-EDIT. M. M.]

MINOR CORRESPONDENCE.

The Almanacs for 1830.-Sir, In the list of the magistracy of London, given in "The British Almanac," page 46, after the "Recorder, Newman Knowlys, Esq.," there appears the "Common Sergeant, T. Denman, Esq." I believe this is the first time the Common Sergeant has been included in such a list; but as he sometimes acts magisterially, I am not disposed to

question the propriety of the addition. If it is,
however, right to include the Common Sergeant,
on this account would it not have been stili
more so to include the Deputy Recorder, Mr.
Sergeant Arabin? And what good reason can
the compilers of "The British" assign for
giving the one a place and excluding the other?
Surely it cannot be because Mr. Common Ser-
geant happens to be a member of the Committee
of Superintendence, under whose auspices this
almanac is issued to the world; or because Mr.
Sergeant Arabin happens to be the rival of Mr.
Denman for the reversion of the Recordership!
I wait for a reply.
I am, &c.
CIVIS.

Ward of Farringdon Within, Dec. 2, 1829. [The suppression of Mr. Sergeant Arabin's name is certainly very indecorous; but we must state at once our firm conviction, that neither the Common Sergeant nor the Committee of which he is a member have had any thing whatever to do with it. Mr. Denman, in particular, is by far too high-minded and honourable a man to countenance so underhand a method of keeping a rival's pretensions out of public view: it is evidently the device of some tool, who thinks by this means to curry favour with his employers.-EDIT, M. M.]

Almanacs for 1830.-Sir, Relying on your as sertion that the Englishman "contains at least one-third more matter than the British," I resolved that the Englishman should be my almanac for the ensuing year; but after purchasing a copy, I was surprised to read in a critical notice of both almanacs, which appeared in that respectable journal, The Times, that the " arrangement" of the British is fully better than the other, and its articles of information "more numerous." I immediately concluded (will you pardon me?) that you had given a false character of your favourite;" but to make sure how the fact stood, I put it in my pocket, and called on a friend who takes in the British, and every thing published by the Useful Knowledge Society, in order to make a fair comparison of the one with the other. We have accordingly gone through them page by page, and the result, which it is but fair you should be made acquainted with, is briefly this:-The number of distinct "articles of information" in the British is eighty five; in the Englishman-two hundred and seven!!! The Times has no doubt been imposed upon by the artful manner in which the table of contents in the British has been drawn up. The Calendar, for example, which passes for one article in the Englishman (as it ought), is there split into twelve!

I am, Sir, your constant reader,
PETER PARTICULAR.

Sir,You are incorrect in your correction of the Englishmau's Almanac in regard to the obligation on the Speaker of the House of Commons to adjourn the House at four o'clock if forty Members are not then present. The Speaker counts the Members silently to himself as they come in, and unless the number of forty is made up when the clock strikes four, he invariably declares an adjournment.

I am, Sir, yours respectfully,
Pall Mall, Dec. 3, 1829.

M. P.
[We find on farther inquiry that the practice
is as our correspondent states; and have to apo-
logise to the compilers of the Englishman for our
impeachment of their accuracy on this point.-
EDIT.]

Sir,-You who pretend to know so much about how almanacs should be written, will perhaps be able to say whether it is any part of the business of an almanac-maker to indulge in impertinent sneers at institutions patronised by some of the first characters in the country. In

the Tradesman's and Mechanic's Almanac ther e is a notice of that excellent establishment the National Repository, the merits of which are thus abruptly disposed of:-" This would have been an admirable institution for the cominencement of the eighteenth century!" The writer might at least have favoured his readers with a reason for this presumptuous assertion.

I am, &c.

L. U. T.

[The writer of the notice in the Tradesman is quite correct. The Repository is, at the very least, a hundred years too late.-EDIT. M. M.]

Jackson's Studs for Boots and Shoes." Wm. Kingsnorth, of 31, Smith-street, Northamptonsquare, Carpenter," desires to corroborate by his testimony the great durability and economy of shoes provided with these studs, which he pro. nounces from experience to be greatly superior to "either metal heels, nails, or sparables." We know Mr. Kingsnorth to be an old and respectable member of his craft, and attach great weight to his recommendation.

INTERIM NOTICES.

"Ingenious but Poor." The mode and expense of taking out a patent for a medicine are the same as for any thing else. Next Session of Parliament will probably decide whether there is to be any reform in either respect.

Mr. Steele promises to send us shortly a letter on a subject which he justly describes as one of "great general importance, not merely to Great Britain and Ireland, but to every country in Europe that sends ships on the Atlantic towards the United States of America, as well as to the American States themselves;" namely, "the formation of an ASYLUM HARBOUR at Carrickaholt, near the mouth of the Shannon."It is inatter of notoriety that a great many ships are lost annually for the want of such a port of refuge.

We overlooked the concluding part of Mr. Hopwood's last letter till it was too late to do as he directed.

The series of papers offered by Brackstone will be acceptable.

T. F. M. deserves great praise.-We shall give his letter and the explanations he requests in an early number.

We presume that Mr. Murdoch and Mr. Hopwood will agree with us in thinking that the letters, inserted in our 329th Number, from Mr. Gilman and R. C. jun., render any farther exposition of the fallacy of the plan for a Selfacting Railway Carriage unnecessary.

Communications received from Mr. Thomas Davy-A. B.-J. R-Caleb Mainspring-In vestigator-Mr. W. Rickett-C. B-k-J. P. W. -Mr. Day-James C.-E. W. G.--Mr. Radde. ley-G. F. S.-Mr. Hebert.

Errata. -In the description of the coachmakers' klam, vol xi. p. 328, the bow is described as 5 feet 8 inches; it should have been of an inch. P. 205, col. 1, l. 8, for B2," read" BE," 602" read 1. 9 and 10, for " "DC2."

P. 258, col. 2, 1. 38, for "experiment," read "expedient."

P. 260, col. 1, 1. 19, for " the nitrogen thus charged with heat," read "the heat thus ab, sorbed by the nitrogen."

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

M. SALMON, Printer. Fleet Street.

Mechanics' Magazine,

MUSEUM, REGISTER, JOURNAL, AND GAZETTE.

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DESCRIPTION OF A PAPER-DRYING APPARATUS EMPLOYED AT THE IMPERIAL PAPER-MILL OF PETERHOFF, IN RUSSIA, INVENTED BY MR. WILLIAM REED.

(Concluded from our last No. p. 275.)

D is a section of the thin copper rollers, which are only hammered by a good coppersmith. Brass ends,

turned and soldered in the four rollers carrying the endless felt, have edges cast on a little lower to allow the double edge of felt to rest on, as it requires guide wheels-three pair on each side to keep it stretched. The reels E are round or square, as required (flat reels we have thrown away).

When the dry paper is wound about 500 times, we cut it off from the reel with knives made of handsaws, backed with a piece of sheet-iron to keep them stiff. Four at a time in use will last

a year, if good.

It may be as well to notice, that in making the first pair of copper rollers, marked No. 2, the copper must be full a quarter and sixteenth brazed and hammered true; otherwise, in turning, the slide-tool will find its way through it before it is round. The brass-tube gudgeons are let in about two inches into the end; drove

very tight, and well soldered; because, on account of the great distance from the bearing required by the driving riggers and valve for escape of condensed water, they would be apt to get slack. I likewise screwed copper

screws through the tube and brass end, and they are now as firm as the first day. At the delivery from the clarionet-valve there is a small tube with a hole in its side to guide or prevent the water splashing or wetting the paper as it falls into the trough marked No. 10. The steamrollers, felt-drum, reels, &c., are all driven by straps from the machinecylinders marked No. 1.

The cost of a set of such steamrollers is about £250, without the boiler; copper in sheets being 11d. per lb. and cast-brass 16d. to 1s. 8d. per lb.

I should have mentioned that the cast-iron forked bearings, No. 9, have on the top a piece of iron with a stout wire pin to keep the roller in its place, and likewise a small funnel for holding suet-it not being so soon melted. If the rollers get dry they

soon cut.

I am, Sir,

Your obedient servant, WILLIAM REED.

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