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NOTES AND NOTICES.

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to which to attach the wire gauze. The part which I have denominated the inverted cone of wire gauze may be a segment of a sphere, as well as of a cone, and may be made to produce the same mechanical effect.

The sparks as they rise from the chimney strike against the wire gauze, and from its position they are carried by the draught up its inclined sides until they come into contact with the under side of the ring, whence they fall, as already stated. The inner edge of the ring may be made to incline downwards, in the direction of the wire gauze. The difference between the action of the draught upon a flat, or a concave surface, in detaining the sparks, and the action upon such a one as I have described will be apparent; as its tendency in the former case is to cause them to adhere to, and in the latter to slide upon the surface, thus perpetually freeing it from their obstructing influence.

ATMOSPHERIC SODA WATER FOUNTAIN ; B. Swan, New York.-An air vessel, or receiver, like the common soda water fountain, is prepared, and placed in a vessel containing ice, to serve as a refrigerator. Into this air vessel is to be forced, by means of a suitable pump, an alkaline solution, made by dissolving an ounce of super-carbonate of soda in every gallon of water. The forcing in of this solution will condense the atmospheric air within the receiver, and cause the solution to flow out when required. Any of the usual varieties of sirop are to be used, with the addition of seven ounces of tartaric acid dissolved in every gallon thereof. About an ounce of this is to be poured into a threequarter pint tumbler, and the alkaline solution then drawn into it.

The claim is to "the placing of a carbonated alkaline solution in a suitable vessel for containing the same, and causing it to pass, as wanted, into a receiver, or air vessel, by means of a force pump, thereby condensing the atmospheric air contained therein, and thus causing it to operate like the common soda water fountain."

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SWINGING BRIDGE, Abner R. Ring, New York. This bridge is to pass over canals, and is to be opened by the contact of the boat, after the passing of which it is to readjust itself. The bridge is to be in two parts, there being a pier in the middle of the canal to support the inner ends of the two sections. These sections turn on pivots on either side of the canal, there being friction rollers, and a circular ring, or hoop, of iron, bearing upon them to sustain the bridge. The boat in passing comes in contact with friction rollers on the ends of levers, which levers give the first impulse in the opening of the bridge. After the passing of the boat, the bridge is to be closed by the action of a volute spring, aided by a counter weight.

Claim. "What I claim as my invention is the combination of the lever and springs for giving the first impulse to the opening of the bridge; the mode of preventing the jar when the boat comes in contact with the bridge, and guiding the boat through by means of the springs and rollers; and the mode of closing the bridge by means of the combination of the volute spring and counter weight, as described."

The plan appears to be devised with skill, and in a model the operation will be very promising, but beyond this we want for confidence. The structure must, we think, be very light indeed, which could be made to act in the way proposed. If the experiment has been successful, however, we shall be glad to hear of it, and to give it publicity.

NOTES AND NOTICES.

Testing by Electricity.-M. Rousseau proposes to ascertain the purity of certain substances, and to detect any adulterations in them, by measuring their conducting power for electricity. Some years ago he described a simple apparatus by means of which the purity of olive oil might be tested on similar principles. He now states that by these means any adulterations in chocolate or coffee may be readily detected: he finds that pure chocolate is a non-conductor or insulator of electricity, but that in proportion to the quantity of farina or fecular matter with which it is adulterated, the more easily does it conduct electricity; and in the same way he states that coffee is an insulator, whilst chicory, with which it is often mixed, is an excellent conductor, and hence the presence of only a small quantity of that substance is easily detected in coffee by its increased conducting power. M. Rousseau also considers that this test may be applied with advantage to the examination of pharmaceutical extracts and preparations, because they very much differ in conducting power, and therefore any mixture or adulteration will be readily discovered.

Trunks of Trees.- In altitude, or length and dismeter, the stems or trunks of trees present the most varied and contrasted features. According to Von Martins, there is a palm that grows fifteen teet high, with a trunk not thicker than the finger. A

comparison, indeed, between the stems of various plants would, in some case, afford examples of widely diverging extremes. The Scirpus Capillaris is not thicker than a hair, and some as fine as a gossamer thread, while the trunk of the paobab is nearly 100 feet in circumference. Even canes and reeds, in foreign climates, sometimes rush up to an incredible altitude. Dr. Walsh cut down one of the canes in the Brazils, called with its congeners ་་ grass of the thicket," and it was found to measure ninety feet in length; it was exquisitely polished and sharply pointed, and felt "lighter than a cartwhip." Amidst the dense gloom of the thicket, and struggling for existence, there is a reed which, though not thicker than a goose-quill, mounts upwards, and overtops the loftiest trees of the forests of India. The "Coque" of Chili threads the woods to an extent of 600 feet.-Economy of Vegetation. Letter Weighing Machines.-The change in our Post Office regulations has set so many ingenious men speculating on the best and most simple contrivance for weighing letters, that the public, like ourselves, is a little perplexed to decide between their several claims and pretensions. Some have proposed to themselves different objects-thus Mr. Hooper, whose instrument we lately noticed, had evidently consulted the breeches' pockets of the thousands who desired only to attain an instrument at small cost: while Mr. Osler, of Birmingham, so well known for his anemometer, and who now puts in a claim to be heard, has taken the select few into consideration, and has produced one, which for beauty and simplicity, we recommend to the attention of the ladies as an ornament to their drawing rooms. It may be briefly described as an upright glass tube, containing mercury, into which is plunged a graduated piston, so that on placing a letter on the top of it, the piston sinks into the mercury in proportion to the weight of the letter, which is ascertained from the graduated scale.Athenæum.-[Mr. Osler's balance appears to be the same as one invented by Mr. Miller of Dundee, and noticed in our Magazine of the 21st ult., No. 854. Ed. M. M.]

Varnish for Iron or Steel.-The Nantucket Inquirer states that "A permaneut varnish is obtained by rubbing iron in a state nearly red hot, with the horny hoofs of cattle, which were previously dipped in a small portion of oil; this process is asserted to afford the best defence from the destructive influence of air and humidity."

The Largest Iron Sailing Vessel in the world was launched on Tuesday the 7th Jan. from the building yard of Messrs John Ronalds and Co. of Aberdeen. It is named the "John Garrod." The length of this noble vessel over all is.. 150 feet. Breadth

Depth...

31 do. 21 do.

And measurement upwards of 800 tons. It is believed that on 14 feet water she will carry 1,400 tons weight. She will be full-shipped rigged; the standing rigging of patent metallic cordage, the lightness and other advantages of which are not yet sufficiently known here to be fully appreciated. -Aberdeen Journal.

Steam-engine Furnace Flues.-Sir,-There appears to be a notable error in Mr. Hartop's paper on flues and chimneys in your useful magazine for last month, where he states that the water at the upper part of a boiler is hotter than at the bottom. Now it is generally believed that the reverse of this is the fact, and that the temperature of the water increases at greater depths in the proportion of one degree of Fahrenheit for every ten inches, measuring from the surface downwards. If so, Mr. Hartop's conclusions respecting the Cornish boilers must be erroneous, yours, &c.,-PENNY POST.

Norwich Port.-Sir,-I find upon reference to the advertisement in our papers relative to "Norwich a Port," the works are to sell, and not to let, as assumed in my communication sent yesterday, and I beg of you to correct it accordingly. I am, &c. Norwich, Jan. 16, 1840. W. THOROLD.

Mr. Jones's Clinometer.-Sir, In answer to Mr. Evans's courteous epistle, I beg to inform him, that in the year 1837, I forwarded to the "Royal Cornwall Polytechnic Society," an excellent working instrument in every particular the exact resemblance of the engraving that appeared of it in your columns a few weeks since, together with an improved trough for washing tin and other metallic ores, by which any loss in the process is completely prevented, and some new machinery for facilitating the ascent and descent of the "Cornish mines,' an engraving and description of which will be found in the Society's report for that year, and for which the Society awarded me a first class honorary medal. I merely mention these circumstances to show that the Clinometer is only one of the many objects to which I have devoted my attention, and that so far from pirating the invention, I was wholly unconscious of any instrument having been made for the specific purposes for which my invention is intended. I am, &c. Wm. JONES.

Values of Various Fuels.-From an extensive series of experiments lately made, it has been ascertained that one pound of Wallsend coals will impart one degree of heat to 8,000 lbs. of water; of Llangenech, to 9,000 lbs.; charcoal, to 10,000 lbs; and of anthracite, to 12,000 lbs.

Russian Manufactures.-To show what progress Russia is making in manufactures, it may be stated, that there are no fewer than one hundred and eighty-seven manufactories of various kinds in or near the capital. Many of these are worthy of especial notice, but we can mention only the celebrated and interesting Alexandrofsky Zavod, which stands about six miles from the city. This is one of the largest manufacturing establishments to be met with on the continent, there being about 3,000 free labourers employed in it, and 1,000 boys and girls from the Foundling Hospital. There is also a house of convalescence for patients from the Foundling, and an hospital for the sick of the place. Cotton, linen, table-cloths, quilts, sail-cloth, and playing cards, are here manufactured on a very extensive scale; the men being employed in the hemp and flax departments, and the children on the cotton and linen. There is also a very extensive fabric of weaving and spinning machinery, steam-engines, &c.: but we were given to understand that (as we have usually found regarding such establishments abroad) the Emperor can procure steam-engines, and all kinds of machinery, much cheaper from England than he can make them at home. The superintendents are from England; and the whole of the works are under the management of a gentleman of the name of Wilson. *Though comparatively little has been doing in them of late years, a visit to the Porcelain Works will also reward the stranger. We have seen some vases which were made here, as large and as beautiful as any of the famous Dresden manufactory. The painting, in particular, is most exquisitely finished. The Glass Works of St. Petersburgh have long been celebrated. Some of the largest mirrors in Europe have been made here, and the labours are still carried on with great spirit.Bremner's Excursions in Russia.

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Erratum.-In page 249, col. 1, line 5, from the bottom, for "but to any two places in the same longitude, and not from the equator," read “but to any two places in the same longitude, and not far from the equator.”—J. N.

LONDON: Printed and Published for the Proprietor, by W. A. Robertson, at the Mechanics' Magazine Office, No. 166, Fleet-street.-Sold by A. & W. Galignani, Rue Vivienne, Paris.

VOL. XXXII.

Mechanics' Magazine,

MUSEUM, REGISTER, JOURNAL, AND GAZETTE.

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ING'S COMMEMORATIVE LETTER BALANCE.

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VICTORIA
AUG 17:1839

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PALMER
AUG 21785

Sir, -The new Post Office regulations have already engaged the attention and ability of many ingenious men, and as the result, a variety of machines for ascertaining the weight of letters previously to posting, are now before the public. It therefore seems necessary to assign a reason for introducing to your notice and that of the public, through the me dium of your widely-circulated Magazine, another letter balance. My object in designing the one now presented, was that there may be something in so necessary an article commemorative of the various improvements in the Post Office establishment.

I consider that the improvements made for the more speedy and safe con

veyance of letters by the mail coaches projected and carried into effect in 1784, by Mr. J. Palmer, were a great national benefit, and the uniform penny postage plan, by Mr. Rowland Hill, is likely to prove a great and lasting advantage to the commercial interest of this kingdom, and that the year in which it received the Royal Assent will be a memorable event in the history of Queen Victoria. You may readily perceive from these observations, that I am of opinion some public monument should be erected by which both the present and future generations may know to whom they are indebted for these arrangements. When I look at the various pillars in the country, and the splendid and appro

KING'S COMMEMORATIVE LETTER BALANCE.

priate monuments in St. Paul's and Westminster Abbey, to the memory of those who have distinguished themselves as Warriors, Politicians, Statesmen, Poets, &c., I have been led to think that some public testimonial is due to those, who,

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in the present day, have employed their time and talents for the improvement of the internal communications of our beloved country; but as I cannot erect a public edifice-I must be satisfied with constructing a useful article, which will Fig. 5.

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associate with it the names of these public benefactors, which may be possessed by every family in the United Kingdom,

and this I call "The Commemorative Letter Balance." By a reference to the drawing, (see front page), you will per

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