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when presented to them. By guiding the wood or stone in a proper manner the drills may be made to cut them into any form required.
This is the general principle. The following is the manner in which it is carried into effect for carving an oak panel. A slab of solid oak is firmly fixed to a flat table which is capable of turning on its centre. On the slab is closely screwed a templet of iron, in which apertures are cut corresponding in form with the parts to be incised in the oak. The revolving drill is supported by a radial bracket, which can swing horizontally, and can be raised or lowered as may be desired when set to work. The workman depresses the drill and brings it to bear on one of the portions of the slab which appears through the apertures of the templet; and by slightly turning either the bracket of the drill or the table, he can bring the drill to act on any part of the slab. Consequently by guiding the drill all round the edge of the aperture of the templet, he speedily cuts a way the wood to an uniform depth and of the exact shape of the pattern.The wood has now been pierced through to the requisite pattern, but the edges of the parts incised are plain and perpendicular to the sunken. These plain edges must be converted into mouldings, and for this purpose fresh drills are substituted, the templet still remaining. These drills vary in shape according to the moulding required; they are, as before, worked round the edges of the pattern, and by undercutting laterally produce the desired forms.
The invention is capable of extension to many purposes beyond those to which it is at present confined ; chimney pieces, furniture of elabo. rate pattern, and articles of slate may be produced at a greatly diminished cost. Carved furniture and paneling which have hitherto been confined to the palace and the mansion, may by these means find place in far humbler dwellings.
The imechanism which Mr. Pratt has constructed for such important objects must be valuable in every respect; and we deem it no small part of the benefit arising from the construction of a great public work like the Palace at Westminster, that men are thereby stimulated to the discovery of such inventions as the present. We should state that the invention is due to a Mr. Irving, who attends to the working of the machinery. Mr. Pratt is now engaged in constructing a roof for Great Malvern Abbey, full of tracery, including the tie beams and spandrels; the dimensions of the roof are 90 st. in length and 30 ft. in breadth; the cost, including the wainscot, will not be more than £1,500, and it is to be finished within eight months after the order was given. The cost of such a roof constructed by manual labour would be at least from £5000 to £6000. A piece of tracery containing 2 square feet and 2 inches thick will not cost more than 14s., including the oak. Ve must not omit to mention that Mr. Pratt has engaged Mr. Billings, well known by his works connected with Gothic Architecture, to attend to the architectural department.
We are informed that the principal part of the decorations in oak of the interior of the New Houses of Parliament is to be executed by the aid of this machinery.
Civ. Eng, and Arch. Journ.
On Improvements in the Manufacture of Glass for Optical Pur
poses. By MR. CLAUDET. Heretofore, the manufacture of glass fit for the purpose of the optician has been a matter involving great uncertainty and difficulty, and in fact it was not until the year 1744 that it was accomplished with any degree of success. About this time, however, a Swiss named Guinand, in making some experiments in the construction of the telescope, found the extreme dificulty of procuring glass fit for lenses; the difliculty led him to endeavour to make glass for himself, and from his labours arose the first process by which glass could be made with certainty sufficiently good in quality for the construction of optical instruments. With the death of Guinand his secret was partially lost. The invention which forms the subject of Mr. Claudet's paper is founded upon the process of Guinand, and is due to a French glass manufacturer named Bontemps, whose attention was first drawn to the subject by the son of Guinand himself. The chief defect in optical glass consisted in striæ and spots; these arose from the great difficulty of properly mixing the materials when in a state of fusion; it was impossible to stir the melted mass, because the temperature was so high as to destroy the instruments of metal, and besides by introducing them into the glass it would have been tinged with color, according to the nature of the metal employed. The method used by M. Bontemps is to introduce the iron rod used in stirring into a clay cylinder closed at one end, so that the glass is entirely protected from the injurious action of the iron; the ingredients are thus effectually mingled; the glass is then suffered to cool gradually, the crucible broken with care, and the mass sawed transversely into slices, so that lenses may be obtained of the diameter of the crucible. Very large lenses have been produced by these means, and two of a metre iu diameter are now in progress of manufacture for the Royal Observatory at Paris.
Trans. Soc. Arts,
Additional Remarks respecting the Condensation of Gases. By
M. FARADAY, Esq. The author, suspecting the presence of nitrogen in the nitrous oxide on which he had operated, repeated his experiments with this gas very carefully prepared from pure nitrate of ammonia ; but the results still indicated the presence of a more volatile gas mixed with another less volatile. He found that olefiant gas is readily soluble in strong alcohol, ether, oil of turpentine, and other bodies of the same kind; and that, like the former gas, it seems to be of a compound nature. His experiments confirm the prevalence of the law that the force of vapor increases in a geometrical ratio for equal increments of heat, commencing at a given amount of pressure. The more volatile a body is, the more rapidly does the force of its vapor increase by an augmentation of temperature; the increase of elasticity being directly
as the volatility of the substance. By further and more accurate investigations, a general law may be established for deducing from only a single observation of the force of any given vapor in contact with its fluid, its elasticity at any other temperature.
Trans. Royal Soc.
Rapid Printing A curious instance of rapid printing has come to our knowledge, which is worth recording. The Lords of the Admiralty ordered that the Nautical Almanac for 1845 should be reprinted. The old edition of 8,500 copies had been exhausted : and, as sometimes happens with this work, copies were selling at twelve times the original price to those who absolutely required them, and had neglected to procure them. The order was given on the fourth of last month, and on the twenty-fourth, only seventeen working days having intervened, complete copies were sent to the binder. This Nautical Almanac contains 616 large octavo pages, of which 572 are filled with numerals, and the rest with small print. The printers, Messrs. Clowes, were (to save time) intrusted with the complete supervision, not a single sheet being sent to the Nautical Almanac Office to be compared with the old edition until it had been finally worked off. The result of careful examination at the Almanac Office, made as soon as each sheet was finally dismissed from the printers, shows a list of 33 errata, or one for every 19 pages: and most of these errata are trivial. Two of them are only wrong rules; nine of them consist in the dropping out of a letter or figure at press, which happens in the most deliberately printed works; one of them is a substitution of a word in capitals for one in Roman letters. Some people will at first imagine that the type of the first edition remained standing, and that the new edition was printed from it. But the first edition was printed four years ago. Truly we have here a striking instance of the power of a printingoffice.
Enamel Portrait on Porcelain. The silver Isis medal was presented to Mr. J. Haslem, for his Enamel Portrait on Porcelain.
In the large enamel portrait of the Duke of Wellington submitted to the Society, the object has been to combine the force and freedom of an oil-painting with the richness of color and brilliancy of an enamel; and the following is the way in which this was executed.
An oval wood panel was procured in the first place, and the portrait painted on it in oils. Two colors only were used for this purpose. In the lights the color was laid on thick and prominent,-in short, it was painted with a considerable impasto. From this painting, when it was sufficiently dry, a mould was taken in plaster of Paris; the porcelain clay was pressed into this mould, and a slab, or plate, thereby made, on the surface of which was an exact impression
of the original painting on the wood panel. After the slab had been fired and glazed, it was painted with enamel colors, in the way highly finished paintings upon porcelain are usually done, i. e. it was first what is called “washed in," and fired in the enamel kiln, painted over again, and fired again, and so on until it was finished. For this purpose it passed through the enamel kiln five or six times.
This portrait should not be taken as a perfect specimen of a new style; it is only a first experiment, and by no means so perfect, as far as the impasto is concerned, as it ought to be. In making the slabs in the first instance considerable difficulty was encountered. As is often the case in making large pieces of porcelain, many were spoiled by breaking, and otherwise, before one could be got to stand the firing. By the time this was done the mould had lost a good deal of its sharpness. The slab afterwards got too thick a coat of glaze, by which the impasto suffered still further. From these two causes the impasto is not nearly so sharp as was intended; consequently the picture has lost a great deal of that crispness which it was anticipated one got up in this way would possess: and probably it has lost from the same cause something in effect also.
Trans. Soc. Arts.
The following extract from a letter from Mr. Finlaison, of Loughton Hall, appears in the Polytechnic Review :—"Mr. Brain has succeeded to admiration in working electric clocks by the currents of the earth. On the 28th of August he set up a small clock in my drawing
. room, the pendulum of which is in the hall and both instruments in a voltaic circuit as follows:-On the N. E. side of my house, two zinc plates, a foot square, are sunk in a hole, and suspended to a wire: This is passed through the house to the pendulum first, and then the clock. On the S. E. side of the house, at a distance of about forty yards, a hole was dug four feet deep, and two sacks of common coke buried in it; among the coke another wire was secured and passed in at the drawing-room window, and joined to the former wire at the clock. The ball of the pendulum weighs nine pounds, but it was moved energetically, and has ever since continued to do so, with the self-same energy. The time is to perfection, and the cost of the mo. tive power was only 7s. 6d. There are but three little wheels in the clock, and neither weights nor spring; so there is nothing to be wound up."
On Robinson's Patent Drying Machine. By J. ROBINSON. This machine was first used in the manufactories of France for the purpose of drying fabrics of wool, cotton, and linen, and was found to produce a great improvement in the color and appearance of the articles passed through it, as well as a considerable saving of labor and fuel.
From the pe
} wrung in 4 minutes ?
It has been used with equal success in this country, as by means of the machine all kinds of scoured and dyed wool, woollen cloths, flannels, stuffs, mousselines de laine, merinos, printed cottons and silks, dyed worsted yarns, &c. &c., as well as all articles requiring bleaching (put into it quite wet,) will be sufliciently dry in six minutes to work and finish off, leaving a suppleness of texture and brilliancy of color unattainable by heat.
Trials of the machine have been made at the Royal Naval Hospitals at Haslar and Plymouth, the officers of which establishments report most favorably of it. At laslar Hospital the result was 1st Trial. 6 Blankets 2 Flannels
riod the ma
chine reached 2d Trial. 9 Sheets
wrung in 8 minutes
its velocity, 28 Shirts
and every part 3d Trial. 15 Blue coats
of the articles 21 pairs of wrung in 4 minutes equally dried Stockings
or wrung. From hanging up in the drying-room, thermometer 101°. A Blanket, thoroughly dried and fit for use, in
1 hour, 23 minutes. A Sheet
41 A Shirt
57 A Blue Coat
45 At Plymouth Hospital the result was,
Ist Trial. 6 Blankets
15 pairs of Stockings} wrung in 6 minutes.
2d Trial. 10 Coats
S 20 Shirts The machine consists of two boxes revolving on an axis with great rapidity, the number of revolutions when at its full velocity being at the rate of 300 per minute. It is set in motion either by cog-wheels or a strap and pulley with an ordinary handle. The boxes are inclosed in an outer case to prevent the water from ilying about, through which case the air enters by means of openings at the sides and ends.
Trans, Soc. Arts.
Method of Preparing Benzoic Acid. By Dr. STENHOUSE. Proceed as in Sheele’s process, by mixing finely pulverized gumbenzoin very intimately with its own weight of slacked lime, also in fine powder. The mixture is to be repeatedly boiled with water so long as any benzoate of lime is dissolved. The filtered liquid is to be evaporated to about one sixth of its bulk, and a considerable quantity of a strong solution of hypochlorite of lime is to be added to it.