Fig. 1. To draw a trefoil parapet between two given distances, it is first necessary to form a horizontal line upon which any number of equal divisions may be marked; when this is effected, describe on each alternate division, as at A, the semicircle в B; the ends of the parapet to terminate with a quarter of a circle. Determine the width of the mouldings в c; then take half the distance between a c, and strike the dotted circle; from 1 strike the dotted line terminating at G; from a strike the arc D E; from the points G strike the arcs H; and from the point I strike the lower arc л, which will give the form required. Fig. 2. Describe the circle dotted at A, then divide it into three equal parts, B B B; on the line c take a division something less than half, for if half were to be taken the circles would overlap, so that the circles meet at the perpendicular line; the contour of the figure will then be produced. The mouldings must now be placed on each side of the one now formed, that being retained as a centre. From the point c strike the semicircle D; and after determining the width of the moulding p, take half the width CE, and strike the semicircle F F. From the points FF strike the arcs G G, and from the point H strike the semicircle E, the arc being struck from the centre of the circle. Fig. 4. Emitation of Foreign Woods. HE art of veneering itself can only be esteemed as being one degree higher in importance than that of staining inferior woods so as to combine the excellence of those of a superior description with the cheapness of the other, must certainly rank; and as every species of information upon such a subject must be extremely valuable, we here present the translation of a paper on the "Imitation of Foreign Woods," presented by M. Morin at a late meeting of the Sociétié d'Encourage Another description of parapet formed by rule as above. First form a triangle, and divide the sides into two equal parts; then draw a line from the centre to the points A A, the intersecting of which will produce the centre B; divide the line from the point в to the triangle into three equal parts, two of which will give the size of the circle D; from the points cccment:describe the arcs c c c, and the form will be obtained. "The colouring of wood is entirely a chemical art, and consists in dyeing the ligneous fibre by the introduction of colouring matters EDGEXPERIMENTS ON CAST-IRON.-Some experi-into the substance of the wood. This art apments made at the Crane Foundry on the re-plied to the woods the growth of our own soil, lative strength of cast-iron, chilled and unchil- has for its object to replace in cabinet work led, showed that the process of chilling gave a and other ornamental purposes, the more exsuperior strength of 17 per cent. The fol-pensive woods which we at present import lowing experiment was tried on four bars, cast in the form of a double-faced railway rail, 14 in. deep, in. wide at top and bottom, and in. in the centre-the length of each bar was 18 in., and 15 in. between the supports. No. 1 was cast in green sand; No. 2 in dry sand; No. 3 cast in a chill; and No. 4 in a chill, and afterwards annealed. No. 1 weighed 32.5 ozs., bore 1,232 lbs., and deflected 130 in. No. 2 weighed 305 ozs., bore 1,008lbs, and deflected 114 in.; No. 3 weighed 34.75 ozs., bore 784lbs., and deflected 053 in.; and No. 4 weighed 34.5 ozs., bore 2,520lbs., and deflected 148 in. The advantages in favour of castiron, treated as No. 4, is evidently little less than 100 per cent. over No. 1, and 300 per cent from foreign countries, such as mahogany, over No. 3. certs over and 300 per growth. such "When I commenced my new researches, the colouring of woods appeared to me to be still in the state of experiment, there being, if I may so say, only a theoretical consumption, without any direct or useful applications. "This want of success in so many instances, in an age when industry is making such rapid strides, has discouraged the greater number of experimenters, and has made it appear that so far as relates to the application of coloured woods to useful purposes, the difficulties were insurmountable; so that for some years the preparation of coloured woods has been almost forgotten or abandoned, and the researches have been directed only to the methods for the preservation of wood, more especially for that employed in the construction of our railways. "I sometimes think that the experimenters have for the most part wanted patience; and that in their researches, too often left to hazard, they have neglected the most elementary principles of organic chemistry, and of vegetable physiology; and have not paid sufficient attention to the modes adopted for dyeing vegetable tissues similar to, or analogous with, those of our indigenous woods. It is by applying the well known and admitted principles of dyeing to the colouring of woods, and by studying the physiological organisation of the wood, that I have arrived at the removal of the difficulties which others have experienced, and have been enabled to place the colouring of woods on what I consider a solid basis. "It has always appeared to me that the most simple and natural plan of colouring wood was to apply the process made use of in dyeing cotton, flax, and hemp, which are all vegetable substances. What, then, is the process employed for dyeing these? We first submit the cotton, the flax, or the hemp, to certain preparatory operations, which have for their object to bring their fibres or their tissues into the best possible condition to receive and fix the colours to be employed; without these needful preparations, dyeing is almost impossible, or if it does take place, neither solidity nor durability are obtained. The same preparation is absoultely necessary for woods, aud hence, in my opinion, the failure of other experiments on the colouring of wood, because they have neglected these preparations. In my researches on the subject, I have had number less difficulties to surmount, for we cannot always apply purely and simply to the colouring of woods the same processes which are used for cotton, flax, and hemp.. Woods in their variable natures and constitutions present different conditions, which it is necessary to take into account in colouring them, nor can blocks and square pieces of wood be managed and treated as parcels or skeins of cotton, flax, or hemp. "The principle of the colouring of woods, thus well established and determined, the next point is to adapt to this principle the modes of impregnation or injection at once the most simple, rapid and economical. I will, now, therefore, enter into some general explanations. "The art of dyeing or colouring of wood, consists of fixing in the vegetable fibre all the colours, as well as the shades of tints, in such a manner as that they will not undergo alteration from the agents to which they are or can be exposed. Air, and especially light, are the most ordinary causes of the alteration of colours, and this alteration depends on the adhesion, more or less powerful, of the colouring matter to the woody fibre. To prepare the wood to combine with the colouring matter, I first submit it to the operations of washing it with an alkaline solution, or of bleaching it (lessivage ou blanchement); this previous operation renders the woody fibre as clean as possible, after which the colouring matter is more readily absorbed, and adheres with greater force to the vegetable fibre. "In certain cases the wood is bleached in order that it may reflect the light in a less degree, and that the tints produced by the colouring matter may become more pure and brilliant. After the washing, follows the introduction of mordants, in order to obtain the colour or shade required. The mordants act as intermediaries between the colouring particles and the woody fibre to be dyed, to facilitate their combination, and at the same time modify their action. "When the wood has undergone these preparations it is perfectly ready to be coloured. It is not always necessary to commence with the washing, especially if it be wished to obtain deep shades or tints; but the washing is quite indispensable when it is wished to remove from the wood all matters which, by their re-action, can in any way modify or alter the colouring effect required to be produced. Thus, for example, tannin being very suitable to render the colours imparted by Brazil wood durable, those kinds of wood which contain tannin should not be washed. But if we require to use a salt of iron in the colouring of a wood, in which the tannin would injure the tints and shades wished to be produced; in that case the washing should be thoroughly performed. I have carried my researches still further, and have endeavoured to overcome the resistance offered in many cases by the woody fibre to the operations of dyeing. It is well known that animal substances have the property of entering most completely into combination with colouring matters, and thus to form colours solid and durable. To communicate this property to woody fibre, the idea presented itself to my mind, of animalising the wood, which I effect by washing it with sheep's dung, or a weak solution of urine, &c. Having thus established the basis of the art of colouring wood, the next consideration is the best method of injection or impregnation. From what has already been said, it will be seen that all the operations of colouring cannot be performed either by simple immersion, or steeping, or by the action of a vacuum, or of pressure in a case or cylinder perfectly airtight, or by vital suction, or by the ordinary methods of filteration. The principle by which I effect the impregnation of wood is not new, but the applications which I have made are new, and the results at which I have arrived appear to me preferable to all others I know. The injection or impregnation is made either by means of an exhausting pump, or a force pump. upon the finger to the middle of it, and the operation be commenced by quickly and "In the former case, one of the ends of the lightly rubbing the surface of the article to be piece of wood is placed in contact with the polished in a constant succession of small cirliquid, and the other end in connection with cular strokes; and the operation must be conone of Stoltz's rotatory pumps. In the second fined to a space of not more than ten or twelve case, the liquid is introduced by the pressure inches square, until such space is finished, exercised on the liquid by means of a force- when an adjoining one may be commenced pump; and I have for these two modes of and united with the first, and so on until the operation expressly prepared apparatus which whole surface is covered. The varnish is will permit the introduction and complete pas-enclosed by the double fold of the cloth, which, sage through the wood of any kind of liquid, by absorption, becomes merely moistened with hot or cold, whatever may be the size or hard-it, and the rubbing of each piece must be conness of the wood." Varnishes. (Continued from page 13.) 70. French Polish. Dissolve one part of gum mastic and one part of gum sandarach in forty parts of spirit of wine, and then add three parts of shell-lac. This process may be performed by putting the ingredients into a loosely corked bottle, and then placing it in a vessel of water heated to a little below 173 deg., Fah., or the boiling point of spirit of wine, until the solution be effected; the clear solution may then be poured off into another bottle for use. tinued until it becomes nearly dry. The rubber may, for a second coat, be wetted with the varnish without oil, and applied as before. A third coat may also be given in the same manner; then a fourth, with a little oil, which must be followed, as before, with two others without oil; and thus proceeding until the varnish has acquired some thickness, which will be after a few repetitions, and depends on the care that has been taken in finishing the surface. Then a little spirit of wine may be applied to the inside of the rubber after wetting it with the varnish, and being covered with the linen as before, it must be very, quickly and uniformly rubbed over every part of the surface, which will tend to make it even, and very much conduce to its polish. The cloth must next be wetted a little with spirit of wine and oil without varnish, and the surface being rubbed over with the precautions last mentioned, until it is nearly dry, the effect of the operation will be seen; and if it be found [The mode of application necessary for that it is not complete, the process must be French polish differs from that of ordinary wine in its turn, as directed, until the surface continued, with the introduction of spirit of varnishes, being effected by rubbing it upon becomes uniformly smooth, and beautifully the surface of the material requiring polishing polished. The work to be polished should be with a fine cloth, and using oil and spirit of placed opposite to the light, in order that the wine during the process. In applying it to effect of the polishing may be better seen. In large surfaces, use a rubber formed of a flat this manner a surface of from one to eight feet coil of thick woollen cloth, such as drugget, square may be polished at once, and the pro&c., which must be torn off the piece in order cess, instead of being limited to the polishing that the face of the rubber, which is made of of rich cabinets or other smaller works, can the torn edge of the cloth, may be soft and now be applied to tables, and other large pliant, and not hard and stiff, as would be the pieces of furniture with very great advantages case were it to be cut off, and therefore be over the common method of polishing with liable to scratch the soft surface of the var- wax, oils, &c. In some cases it is considered nish. This rubber is to be securely bound preferable to rub the wood over with a little with thread, to prevent it from uncoiling when oil applied on a linen cloth before beginning it is used; and it may vary in its size from one to polish; but the propriety of this method is to three inches in diameter, and from one to very much doubted. When the colour of the two inches in thickness, according to the wood to be polished is dark, a harder polish extent of the surface to be varnished. The varnish is to be applied to the middle of the may be made by making the composition of flat face of the rubber by shaking up the bottle one part of shell-lac, and eight parts of spirit containing it against the rubber; it will absorb a considerable quantity, and will continue to supply it equally, and in a due proportion to the surface which is undergoing the process of polishing. The face of the rubber must next be covered by a soft linen cloth doubled, the remainder of the cloth being gathered together at the back of the rubber to form a handle to hold it by, and the face of the cloth must be moistened with a little raw linseed oil* applied * This may be either coloured with alkanet root or not. work polished by the French polish, the of wine, and proceed as before directed. For recesses or carved work, or where the surfaces are not liable to wear, or are difficult to be got at with the rubber, a spirit varnish made without lac, and considerably thicker than that used in the foregoing process, may be applied to those parts with a brush or hair pencil, as is commonly done in other modes of varnishing." French polish is not proper for dining tables, nor for anything where it is liable to be partially exposed to considerable heat.] (To be continued.) Artistic Societies SOCIETY OF ARTS. plied to; gradually it became more extensively known; Baron Aretin, in Munich; Count Lastegrie, in Paris; and Mr. Ackerman, in London, fostered the rising art. In 1819, Sennefelder's account of lithography appeared, LITHOGRAPHY.-At a meeting of this society the frontispiece being a portrait of the author, on the 22nd ult., Mr. S. Williams read a executed by himself; the countenance, it may comunication "On the Progress of Litho- be remarked, exhibiting an indomitable will graphy in England," and observed that litho- and energy. Mr. Hullmandel, who also pargraphy was an art comparatively new to us, takes largely of the persevering skill and scarcely half a century having elapsed since patience of his predecessor in this art, was the its discovery and introduction; yet how rapid, first to perceive that the difficulties that prehow brilliant, had been its progress! To the vented the progress of lithography, were great masses of the people, who were more chiefly of a chemical nature; he, therefore, familiar with, and more accustomed to, the studiously applied himself to the study of that highly-finished productions of the steel-en-science, and, having mastered it, introduced graver, lithography was new, and was too many important improvements. The first apt to be regarded as an accessory of art. work published under his superintendence, Lithography had however attained, and was was a series of views illustrative of Belzoni's well deserving a far higher position; it was an travels. The stone most favourable for lithoally, not an enemy to engraving. In its pre-graphic purposes, is a calcareous slate pecusent state, the artist could by its aid produce liarly tenacious of grease, and imbibing water pictures conveying his peculiar style and char- with avidity. Stones of the best quality are acter, that the engraver could never hope to procured from the quarries of Solenhoffen, in approximate. The discovery of lithography Bavaria, much of the beauty of the drawing was, like that of many other important inven- depending on the goodness of the stone. tions, the effect of accident. About the year Among many others that have been tried as a 1795, Sennefelder, an actor of some preten- substitute for the Bavarian, is the Bathlias; sions to histrionic fame, who had quitted the but this has been found too soft. To an artist stage to become dramatist, being in needy with a feeling for his art, a free and vigorous circumstances, and not having the means to hand, a keen perception of form, lithography print his productions, was in the habit of writ- offers peculiar advantages; and the success that ing them backward on plates of copper, with has attended even the first efforts of those posa hard greasy ink, and from these taking im-sessed of these qualifications, is certainly an inpressions on paper. Copper being too expen- ducement to artists generally to make the atsive, he next tried tin, but with little success. tempt. The drawing having been made with a He then had recourse to Kelheim-stone. He hard greasy ink, the printer subjects the stone to procured these in slabs, polished them, and the action of dilute nitric acid, leaving the drawcovering them with a composition, wrote uponing slightly in relief. The stone is then washed them with a steel-pen, and applying acid, bit with turpentine, leaving only the grease in the in the writing. From these he took impres- stone. In this state it is ready for press. Presions. But this was not lithography; etching vious to taking impressions, a wet sponge is on stone having been practised long before. passed over the surface of the stone; as the Accident, however, revealed to him the true grease in the stone repels the water, so the method. He says, "I had just succeeded in water in turn repels the greasy ink. Considermy little laboratory in polishing a stone-plate able nicety is required in the manipulation, which I intended to cover with etching and attention to the minutiae connected with ground, in order to continue my exercises in this art: thus, if the granulated surface of the writing backward, when my mother entered stone is too open, the drawing will be coarse; the room, requiring me to write a washing bill, if too fine, the light tints will be clogged up; it so happened there was not a morsel of writ-in short, the drawing should be executed with ing paper or ink at hand, nor had we any one a light free hand, and at once, as it cannot be to send for a supply of these materials. As the retouched without injury. Again, if the acid matter would admit of no delay, I resolved to is too powerful, the tints will be bit away; if write with my ink, prepared with wax, soap, too weak, the dark tints will be dull and heavy. and lamp-black, upon the stone I had just The various methods used in the practice of polished; some time after requiring this stone lithography were explained. Our limited for use, the writing being as I had left it, it space will not permit us to follow these in their occurred to me whether I could not bite in the details. In the chalk mode, the drawing is made stone with acid, leaving the writing in relief; with hard black grease on a granulated stone. and thus was lithography discovered. Here, In the ink mode, liquid grease is used. In again, however, Sennefelder was is another the engraved mode, the surface of the stone difficulty he was without the means to turn is incised with an etching point, and the incihis invention to any benefit to himself, being sions filled with grease. In the transfer mode, unable to employ a printer to carry out his the drawing is made on prepared paper, and ideas; he, therefore, determined to become a from thence transferred to the stone. Mr. journeyman printer and learn for himself. The Hullmandel introduced a method of graduating sight of a sheet of music in a shop window, the neutral tints. This important improvement induced him to apply his new art to this pur- enables the artist to produce very beautiful pose, and the printing of music was the first atmospheric effects. Harding's "Sketches at subject that lithography was practically ap- Home and Abroad," Roberts's, Stanfield's and |