During the period in which this Volume has been paring through the prat, tome new matters hating rotation to tit page* have been published; a few of them art here noticed, and by aid of the references in the body of the work, these Notes will
Note A. - To follow the end of page 40.
The Patent Wood Carving. This is not accomplished in the usual manner, by cutting away the wood with chisels, but it is burned away, or rather converted into charcoal. The oak, mahogany, rose-wood, horse-chesnut, or other wood, is steeped in water for about two hours ,* and the oast-iron dye or mould containing the device, is heated to redness or sometimes to a white heat, and applied against the wood; either by a handle as a branding-iron, by a lever-press, or by a screw-press, according to circumstances; the moulds are made by the iron-founder from plaster easts of the original models or carvings.
Had not the wood been saturated with water it would be ignited, but until the moisture is evaporated it is only charred; it gives off volumes of smoke, but no flame. After a short time the iron is returned to the furnace to be re-heated, the blackened wood is well rubbed with a hard brush to remove the charcoal powder, which, being a bad conductor of heat, saves the wood from material discoloration; and before the re-application of the heated iron the wood is again soaked in water, but for a shorter time, as it now absorbs moisture with more facility.
The rotation of burning, brushing, and wetting is repeated ten or twenty times or upwards, until in fact the wood fills every cavity in the mould, the process being materially influenced by the character and condition of the wood itself, and the degrees in which the heat and moisture are applied. The water so far checks the destruction of the wood, or even its change of any kind, that the burned surface simply cleaned by brushing, is often employed, as it may be left either of a very pale or deep brown, according to the tone of colour required, so as to match old carvings of any age; or a very little scraping removes the discoloured surface. Perforated carvings are burned upon thick blocks of wood, and cut off with the circular saw.
The patent mode is considerably cheaper than ordinary carving, and the more so the greater the complexity and delicacy of the design. The date of the Patent granted to Messrs. A. S Braithwaite and Co. for this novel process is Nov. 1840.
Note B. - To follow the Foot Note on Page 116.
Subsequently to the extract from "Dr. Bourcherie's Memoir on the Pretervation of Woods" having been printed upon pages 113 - 116 of this work, the subject came under the notice of the Institution of Civil Engineers; and injustice to the prior claim of Mr. Bethell, I have quoted the following paragraphs from the Minutes of Proceedings of that Institution for 1842, page 88 - 8.
" Mr. Bethell remarked that the process described in Dr. Boucherie's pamphlet was identical with that patented by him July 11th, 1888, two yean before Dr. Boucherie's was mentioned in Paris, which was in June 1840. The specification filed by Mr. Bethell stated ' that trees just cut down may bo rapidly impregnated with the solution of the first class, hereafter mentioned, (among which is included the pyrolignite of iron,) by merely placing the butt ends in tanks containing the solution, which will circulate with the sap throughout the whole tree; or it may be done by means of bags made of water-proof cloth affixed to the butt ends of the trees and then filled with the liquid.' - See Specification in Repertory of Patents, March, 1842.
"Mr. Bethell found that some solutions were taken up more rapidly by the sap and circulated with it more freely than others, and the pyrolignite of iron seemed to answer best; he had not hitherto introduced the process in England because it was much more expensive than the oil of tar, the pyrolignite costing from 6d. to 9d. per gallon, and the oil being delivered at 3d per gallon."
"In answer to a question from Mr. Pellatt, Mr. Bethell stated that his experiments on the use of silicate of potash or soluble glass for rendering wood uninflammable were not yet concluded: he had proved its efficacy in this point - that as soon as the prepared timber was heated, the glass melted and formed a filmy covering over the surface, which protected it from the oxygen of the air and prevented its catching fire. The silicate also hardened the wood and rendered it more durable. This process was included in his patent of July 11th, 1838."
Note C, (and also D, E,) to follow the Foot Note, page 234.
"On some peculiar Changes in the Internal Structure of Iron, independent of, and subsequent to, the several processes of manufacture." By Mr. Charles Hood, F.R.A.S., etc. This paper was read before the Inst. Civ. Eng., 21 June, 1842.
"The singular and important changes in the structure of iron, which it is the object of this Paper to explain, are those which arise in the conversion of the quality of iron, known by the name of 'red short iron,' which is tough and fibrous, into the brittle and highly-crystallised quality known by the name of 'cold short iron.' " - "The principal causes which produce this change are percussion, heat, and magnetism, and the author traces through a great number of practical cases of ordinary occurrence, the joint as well as the separate effects of these three causes; showing that the rapidity of the change is proportional to the combined action of these several causes, and that in some cases where all three causes are in operation at the same time, the change of structure is almost instantaneous; while in other cases, where this united operation does not occur, the change is extremely slow, extending over several years before it becomes sensible."
Various fractured specimens were shown to the Meeting, by which the coarse crystalline structure was principally ascribed to the cold hammering and planishing. See Minutes of Proceedings Inst. Civ. Eng. Pages 180 - 184; transcribed in Civil Eng. and Arch. Journal, 418.