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far as the transport of merchandise may be im peded, the evil would only be the same as is now commonly suffered from canals; but when the conveyance of passengers or correspondence shall be taken into consideration, the objections to inclined planes became strong, if not insu perable.

A multiplicity of machinery is the great evil to be avoided; and experience teaches us, that the daily expense may be diminished in proportion as our power is simplified and concentrated."

It follows from what we have stated of the dates of Mr. Gray's speculations, that we must have been somewhat in error in stating, as we did in our 325th number, that it was the Scotsman newspaper which "had the honour, four years ago, of first bringing forcibly under public notice the advantages derivable from locomotive carriages on railways." But while we frankly admit that in making this statement we overlooked the prior claims of Mr. Gray, we presume it will not be disputed, even by Mr. Gray himself, that it was the papers in the Scotsman which first made that desirable impression on the public mind which Mr. Gray's labours were intended, but had not the good fortune to produce. The reason of this it is not difficult to trace. Mr. Gray's writings on the subject have been mostly of too vague a cast, made up of statements which, though correct in the main, have not been sufficiently proved, and of conclusions rather in the nature of plausible guess-work than of verifiable calculation. The papers in the Scotsman, on the contrary, embraced the whole pith and marrow of the subject; were very circumstantial, distinct, and clear; calculated for popular comprehension, and yet so grounded in scientific principles as to command the assent of the most learned and profound.

MANUFACTURING CLOTH FROM WOOL, BY FELTING, WITHOUT SPINNING OR WEAVING.

Numerous attempts are now making in the United States to manufacture woollen cloth by felting, in the manner of hats, without either spinning or weaving. In the latest list of American patents we observe no less than five for this purpose; and large sums are said to have been al

ready invested by our Trans-Atlantic friends in this sort of manufacture.

One of the most enthusiastic, and we believe the earliest of these patentees, a Mr. Wm. Harrington, of New York, thus expresses himself on the subject:

"I do not claim as my invention any one of the machines used in the herein-described method of manufacturing woollen cloth, nor any particular part of any one of the machines; but I claim that I am the first person who by passing sheep's wool through the above-described or similar operations, and by a combination of the above-described or similar machinery, has been able successfully to manufacture woollencloth of sufficient firmness of texture, strength, and durability, to answer the valuable purposes named in this specification, (viz. carpeting, floorcloths, rugs, table-covers, blankets, padding, &c.) without spinning or weaving, upon the principles of felting. The subscriber is not aware that any one has heretofore been able successfully to avail himself of the well-known felting properties of sheep's-wool for the purpose of manufacturing cloth suitable for carpeting, and other valuable purposes named in the specification."

Mr. Raymond, of New York, another of these patentees, affirms that by his plan of operation" cloth may be made of any desirable length and width, and suitable for carpets, blankets, rugs, gentlemen's wear, and other purposes, in greater perfection, with inore dispatch and less expense, than by any other method."

Confident as these statements are, we apprehend they will be found very delusive. The notion of manufacturing cloth by felting is but a revival of an English project, long since tried and exploded. About forty years ago it was made a fair trial of by several English manufaeturers, but eventually abandoned by all of them, because the cloth made in this way was much inferior to what the loom produced. Neither do we see any thing in the modes proposed to be adopted by the American patentees, which should lead us to anticipate that their efforts will be af

tended with any better result. It is not, in truth, in the nature of things, that felted cloth should ever be of so firm and durable a texture as that which is spun and wove.

FUR

COMPARATIVE EFFECTS OF BLOWING
HOT AND COLD AIR INTO
NACES.

We took notice in our 308th Number, p. 336, of certain experiments of a Mr. Nelson, of Glasgow, which were said to establish the great economy of blowing hot instead of cold air into a furnace; and we then expressed an opinion, to the effect that the expense of making the air hot in the first instance would be found exactly to balance the subsequent gain. We now extract a farther statement on the subject from the Glasgow Chronicle, which is very much at variance with this opinion. Facts are stubborn things certainly, but we must confess that we are still at a loss to discover the sufficient reason which governs the present case.

"Since we last noticed the application of heated air to blast furnaces, experiments with it have been steadily persevered in at Clyde Iron Works, and the result is highly satisfactory. It is completely ascertained by these experiments that iron is smelted by heated air with three-fourths of the quantity of coals required, when cold air, that is, air not artificially heated, is employed for that purpose, while the produce of the fur nace in iron is, at the same time, greatly increased. All the furnaces at Clyde Iron Works are now blown with it. At these works the air, before it is thrown into the blast-furnaces, is heated to 220 deg. Fahrenheit, in cast-iron vessels placed on furnaces, similar to those of steam-engine boilers. It is expected that a higher temperature than 220 deg. will be productive of a proportionally increased effect. But this is still the subject of experiment. It is calculated that this improvement will accomplish a saving in the cost of the iron smelted in Great Britain to the amount of, at least, 200,0007. a-year. The fact that heated air is better adapted than cold air to promote combustion is now incontestably established by experiment. No argument to the contrary is afforded by what is also the fact, that a fire burns better in cold than in warm weather. The fire burns better in the former than

335

in the latter case, not because the air is cold, but because it is dry. Let cold air be artificially heated, and its superiority in promoting combustion over air naturally of the same temperature, but not artificially heated, will be apparent. It has been attempted to account for this fact in various ways. The most simple theory seems to be, that air is not fitted to promote combustion till it reach a high temperature, and that a quantity of fuel is expended in raising it to this temperature before it can be of any use in promoting combustion. The question, therefore, so far as concerns the saving of fuel, in the smelting of iron, resolves itself into this-whether it is most economical, in respect of fuel, to heat the air in the smelting-furnace, where it comes into contact with the coke, and carries it off in the form of carbonic acid gas, or to heat it previously in a separate furnace. The experiments at Clyde Iron Works show that it is heated in the separate furnace with one-eleventh part of the fuel that is required to heat it in the smelting-furnace, when allowed to come in contact with the coke. One reason why that should be the case is very obvious: in the smelting-furnace the air is heated with coke, in the separate furnace with coals. These observations do not apply to the mode of heating the air in a close vessel, by means of the smelting-furnace itself, before it is allowed to come in contact with the coke. The experiments with respect to this mode of heating air are still in progress."

Enquiry.

Sir,-Do me the favour to insert the following query; and if any of your readers will answer it in the course of next week (as I am going to Valparaiso early in January), I shall feel greatly obliged.

I am, Sir, your obedient servant,
AQUEDUCT.

Upper Clapton, Dec. 29, 1829.

If a leaden pipe half an inch diameter in the bore were filled with water, and laid in a straight horizontal line from a reservoir whereof the level of the surface is 30 feet above the discharging orifice of the pipe, with what velocity would the fluid issue from the pipe at the distance of 20 miles from the reservoir? And with what velocity at half the distance? And at three-fourths of the distance? Also at ten times the distance, viz. 200 miles ?

336

MINOR CORRESPONDENCE.

Jackson's Studs for Boote and Shoes.-We have forwarded the letters of Mr. B. Foster and Mr. William Hardcastle, bearing testimony to the merits of these studs, to the patentee, and must decline inserting any more letters on the subject, except by way of advertisement on our mouthly covers. It must suffice to say on our own parts, once for all, that we think the invention a very excellent one, and deserving the patronage of all, to whom a sound, durable, and comfortablewearing boot or shoe is an object.

Callet's Tables.-Mr. Utting requests us to point out the following erratum in Callet's Table of the Logarithms of Sines and Tangents, intended to accompany Mr. Babbage's Table of Logarithms:

In the log. tang. of 24/ 54/, for 7.8599831, read 7-8599331.

A Case for Mr. Hebert.-Sir, M. Peclet relates, that a few days after the steam-boiler, designed to heat the Exchange in Paris, was brought into use, it was perceived that there was a hole in the bottom of it. The fire was extinguished, and it was found on emptying the boiler that the metal was burnt in a place where a piece of rag had been deposited, but overlooked when the boiler was filled with water. Now, I should like to know from Mr. Hebert, to what cause he would ascribe the failure of the boiler in this case? Will he tell us that this all comes from heating by steam? Surely not; and yet there would be no more absurdity in his blaming the heat instead of the rag in this case, than there was in his ascribing the accident which befel "The Novelty," to the bellows instead of the feed-pump.

I am, Sir, &c.

Q. IN THE CORNER.

A Remonstrance.-Sir, You are pleased in your review of "The British Almanac for 1830," (see Mechanics' Magazine, No. 328, p. 216,) to say that the compilers" have ventured this year, with the help of a pair of globes, and of such other lights as are common to the sphere of seminaries for young ladies and gentlemen, to give on their own authority the positions of the principal stars and planets for each month." I must be allowed, Sir, as one of the class to whom you make this not very liberal allusion, to observe that you do them great injustice by the comparison. The "lights" common to our sphere may be not very brilliant, but they are at least considerable enough to prevent the least informed amongst us from committing such astronomical blunders as are common to "The British." No preceptress who teaches the use of the globes would have thought of selecting, as the compilers of that almanac have done, an hour for observation when it seldom happens that more than one of the planets are in sight; or could possibly have descended to the quackery about the Right Ascension with which each left. haud page of the calendar commences (for, taken in connexion with problems on the globes, very clumsily solved, it is in truth gross quackery); neither would such a person (I guess) have thought of inserting the Table of the Sun's Parallax, given at p. 6, from its utter unfitness for the place, than she would have thought of introducing directions for pickling cucumbers. Pray, Mr. Editor, let it be known in some way or other, that there is nobody, even in "the sphere of seminaries for young ladies and gentlemen," who would not be ashamed of such things; and oblige your constant reader and fervent admirer, A GOVERNESS.

Clapham, Dec. 23, 1829.

MISCELLANEOUS.

Large Still-The largest condenser for dis tilling gin ever manufactured has just been made for Mr. Hodges, by Mr. Joseph Hulls, of High Wickham. Its height is 14 feet 6 inches; its dimensions 8 feet. It is calculated that it will distil 10 gallons per minute, 6000 per day, or 1,878,000 per annum.-Morning Herald, The productive capacity of this still is by no means so unrivalled as represented. In many Scottish distilleries, where alembics are employed from 52 to 54 inches in diameter and about 8 in depth, no less than eighty gallons are produced every three minutes and a half.

Economic Lighting.-At the Tulloch, Bleachfield, a young man, named A. Reed, has constructed an apparatus by means of which he is enabled to procure from the wood which they are in the practice of burning in order to obtain acetic acid gas, sufficient to light the whole premises. By this ingenious device a most im portant saving is effected, since no more wood is necessary for both the gas and the acid than was formerly used for the acid alone.-Glasgow Chronicle.

INTERIM NOTICES.

We are constantly receiving so many letters from individuals containing mere announcements of inventions, without any description of them, and having generally for their sole object to bring them under the notice of persons who may purchase or take a share in them-communications which are in fact purely commercial, and which, if inserted, would subject us to the advertisement-duty-that we feel under the necessity of laying it down as a rule, that all letters of this description can only be inserted as advertisements on our monthly covers, and must be paid for as such.

S. P. W. is requested to send to our office for a note addressed to him.

Communications received from C. H.-J. T. H-e-G. W. J.-Mr. Baverstock-E. S. L.T.-M. J.-Mr. Butterworth-Clyde-A Joiner -A Berkshire Mechanic.

Errata in a few of the Copies of last Number.

Page 307, column 1, line 20, for Vanloue,' read Vauloue.'

P. 310, col. 1, line 28-29, for' annalyst,' read ' analyst.'

P. 310, col. 1, line 40, for 'slip,' read 'skip." P. 310, col. 1, line 46-47, for he cannot bring any one of his modifications to accord with,' read' he cannot bring more than one of his modifications to an obvious comparison with.'

P. 310, col. 2, line 33, for varies,' read 'so varies.'

P. 310, col. 2, line 43, for verily,' read 'verify.'

P. 311, col. 1, line 16, after distances,' add 'declinations.'

P. 312, col. 1, line 15 from the bottom, for 'practical,' read physical.'

P. 312, col. 1, line 10 from the bottein, for 'm/P 3 'mP3 read m/P/3.'

m' P'3'

Fig. 1. A is an air tight box, which is supplied with air through the pipe C from the bellows B: on the top of the box are inserted the small pipes DDDD, having each of them at the top an harmonicon with only one tongue each (of course the harmonica must be modulated as a piano-forte). When the notes are to be produced the keys EEE must be depressed, which allow the air to pass through the harmonica. I have drawn on a larger scale, fig. 2, one of the keys which must act as those of a flute. A is the key; D a stop, covered with wash-leather to prevent the harmonica from vibrating; C a spring which must be made strong enough to prevent the air from raising the stop when the box is filled with air; Ba small block in which the key is inserted, and confined by a pin passing through them both. Fig. 3, represents also, on a larger scale, the harmonicon. A is the harmonicon, which for convenience ought to screw off the cylinder C at B.

N. B.-The ends of the keys terminate like those of a piano-forte; in fact, the exterior is exactly like one.

ON THE REMOVAL OF DEPOSITS OF EARTH IN TIDAL RIVERS, AND THE PROBABLE EFFECTS OF REMOVING THE OLD LONDON BRIDGE. BY O. C. F.

Sir,-The subject of the tides, upon which you have lately been saying so much, and with such comprehensive and scientific views, is one to which you cannot too frequently invite the attention of the inhabitants of the metropolis, and the proprietors of estates on both sides of the Thames, for four or six miles above London Bridge.

In your able examination of the merits of different almanacs (No.

329, p. 232), after specifying the difference between the times of highwater immediately above and below London Bridge, you ask, "Is there not great reason to apprehend that when the old bridge is removed, a great alteration will be produced in all these respects?" There is, indeed, so great reason to apprehend that the alterations will be very important and serious, that I cannot but wonder the thousands who are deeply interested. in the result, do not set themselves to inquire what will probably happen.

Mr. Smeaton (to whose valuable reports you refer in your exposure of the extraordinary blunders of Mr. Lubbock) in his letter to the Lord Mayor, Aldermen, &c., on the state of London Bridge, dated 23rd June, 1767,* speaks thus

"It is difficult at this time to determine whether the bed of the River Thames was as high above London Bridge before London Bridge was first erected, as it now is; and whether the stoppage of the water at the bridge, acting as a dam, was an expedient to retain more water in the river at low water over those shoals for the sake of navigation; or, whether this stoppage arising from the obstruction has, in its effects, occasioned the sullage of the river gradually to gather, and the bed to rise nearly in the same proportion as the water's surface at low-water is kept higher? However this might be, 'tis certain the bed of the river above bridge is now, in proportion, higher than it is below bridge.

"If London Bridge were, therefore, to be taken away, the river would become so shallow above bridge at lowwater, that the navigation would be greatly impeded FOR HOURS each tide!"

Residing near London, and being personally concerned in the general question, I often attended the Committees of the House of Commons on London Bridge, in 1822, and well remember the substance of the evidence given by several scientific men on that occasion. Amongst others to whom I listened, the sentiments of Dr. Gregory, of the Royal Military Academy, completely accorded with

Smeaton's Reports, vol. ii. p. 23.