1843.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



207 



of potash or soda, by means of a brush. It is in this manner that walls, 

 constructed of chalk and mortar, may he hardened. Sculpture, and various 

 Other objects, which may he made or prepared in chalk, may be hardened, 

 and afterwards serve for decorating buildings, and other purposes, without 

 the fear of their becoming injured by frost or damp. Chalk, hardened iu 

 this manner, may also be used as a substitute for the stones now employed 

 by lithographers. Plaster models may also be hardened, by placing them, 

 for some time, in a solution of the silicate ; but it would be still better to 

 add a portion of the solution to the paste, at the time of making the model, 

 or using the plaster. The silicate of potash or soda is prepared by fusing 

 one part of white siliceous matter with from one and a half to two parts of 

 potash or soda, in the ordinary reverberatory furnaces, or in a glass-maker's 

 or iron crucible. The solutions may be used of any density for plaster ; but 

 they should be weaker for chalk. In the last place, the inventor has found 

 that the silicates of potash or soda, when dissolved in water, decompose 

 spontaneously in the air, and cover the objects, to which their solution has 

 been applied, with a strong covering or layer ; therefore, by applying the 

 solution of silicate of potash, or of soda, to polished iron, and allowing it to 

 dry in the air, the metal is preserved from oxidation. By soaking wood 

 many times in this solution, and allowing it to dry in the open air, every 

 time after it has been placed therein, it becomes so much penetrated with 

 silica, that it acquires a considerable density and degree of indestructibility. 



The solution of the silicate of potash is not the only substance which, by 

 being injected into porous bodies, tends to harden them. A mixture, made 

 from a solution of bicarbonate of ammonia, and of chloride of magnesium, 

 may be successfully employed ; or a mixture of the solutions of ammonia 

 and chloride of calcium may be used. Iu these latter cases, instead of 

 having siliceous injections, they are either magnesia nor calcareous. Soft 

 and porous stones may also be considerably hardened, and defended from the 

 action of damp, by first well drying them, and then dipping or steeping 

 them iu sulphur, or some natural or artificial resinous or bituminous sub- 

 Stance, rendered liquid by heat. 



The patentee claims, Firstly — the application of certain new means, to 

 change or convert all descriptions of lime into hydraulic limes and ce- 

 ments, or such as become hard under water, or when exposed in damp 

 situations, by combining these limes and cements, with silica, alumina, 

 the oxide of manganese, or the oxide of iron, either by the dry or 

 humid method. Secondly — the manufacture of hard artificial stones from 

 chalk, plaster, and all porous stones in general, by injecting into them, 

 or imbuing them with silica, or the carbonates of magnesia or lime, 

 by any of the above-described processes ; or by causing them, by virtue of 

 their porous nature, to absorb either melted sulphur, or bituminous, resinous, 

 or fatty matters, properly liquified by means of heat. Thirdly — in the em- 

 ployment of the silicates of potash or soda, for making or forming a stony 

 plaster or coating upon a variety of substances ; thereby preventing iron 

 from becoming rusty or oxidized, and rendering wood and other organic 

 matters harder, and not liable to decay. — [Inrolled in the Petty Bag Office, 

 September, 1841.] — London Journal. 



PROCEEDINGS OF SCIENTIFIC SOCIETIES. 



INSTITUTION OF CIVIL ENGINEERS. 



February 3. — The President in the Chair. — (Continued.) 



The Thames Tunnel. — Sir M. Isambard Brunei presented a design intended 

 to illustrate the mode of securing the poliug-hoards of the shield of the 

 Thames tunnel. The poling-boards, shown in the drawing, he described as 

 being intended to close the whole area of the excavation in the front, as the 

 side and top staves were intended to secure the sides and top of it. The 

 shield (weighing nearly ISO tons) in passing over the ground, served mate- 

 rially to compress it, and make a firmer foundation for the tunnel. When it 

 was considered that the mass of ground removed weighed 63,000 tons, while 

 the brick structure by which it was replaced weighed only 26,160 tons; 

 some idea might he formed of the difficulties which had been encountered in 

 the progress of this undertaking. It would be seen by reference to the early 

 reports, that 540 feet of tunnel had been made in the course of sixteen 

 months, viz., from the 1st of January 1826, to the 27th of April 1827. At 

 that period the miners and bricklayers struck, without even securing their 

 work. In this emergency, after standing still a week, new hands were en- 

 gaged ; the result was, that on the 11th and 12th of May, the ground 

 showed symptoms of giving way, and on the 18th the river broke in and 

 completely filled the tunnel ; the length of brickwork then completed was 

 about 550 feet. He was convinced that no irruption would have occurred 

 but for the desertion of the men, for at no previous period had so much work 

 been done; the average progress being 12 feet per week for sixteen weeks, 

 and having at that time the advantage of his son's services and those of ex- 

 perienced assistants, the work might have continued, and the tunnel would 

 have been finished in about four years. After this irruption, an advance of 

 only 50 feet was made within the period of the year 1827, and in conse- 

 quence of a second irruption, the work was totally abandoned. In the year 

 1835, after a lapse of seven years, being liberally assisted by the Govern- 



ment, a new shield was provided, and the work was resumed in the begin- 

 ning of March 1836. The work, however, proceeded very slowly as con- 

 trasted with former periods. On the llth of June the water broke in and 

 continued to trouble the works for six weeks. Having succeeded in repelling 

 this attack, the progress for the whole year amounted to 117 feet. Fore- 

 seeing that he should at some future period, have to account for the causes 

 of these delays, Sir Isambard instituted, in the course of the year (1836;, 

 distinct sets of records for every branch of the service, afloat as well as 

 underground, in order to place beyond doubt, the circumstances which might 

 not otherwise be credited. These registers enabled him to give the minutest 

 details of the work, and would, he hoped, he found useful in any future 

 similar undertaking. Through the whole of the year 1837, the progress was 

 only 28 feet 4 inches, a rate which hardly exceeded that of a fortnight of 

 the year 1827. Two irruptions took place within the range of eight feet, 

 owing to the looseness of some portions of the strata, which were so fluid, 

 that the only expedient for advancing, was by forcing forward some of the 

 polings with the screws. The frequent bursts of gas at that period, and in 

 1838 and 1839, had moreover such an eflfect upon the men, that some of 

 them fell senseless at their post. There was therefore great risk of the 

 poling boards falling down, as had been the case before, and causing a total 

 disruption of the ground. In this dilemma, the expedient of connecting the 

 poling boards with each other by hooks was resorted to, forming by this 

 means a complete panel in the face of each of the 36 cells of the shield ; 

 the top poling being suspended to the head of the cell, the panel could not 

 be disturbed even with a cavity in front of it ; there was likewise an addi- 

 tional means of supporting the polings, by iron spurs resting upon the floor- 

 plates and going into the ground. Notwithstanding the apparent increase of 

 labour occasioned by this addition to the poling-boards, good progress was 

 made, amounting to 240 feet in the course of twelve months, and the hook- 

 ing was found so safe iu its service and its results, that were another tunnel 

 to he constructed, Sir Isambard stated, that be would make the system of 

 attaching the poling-boards, an essential part of the organisation of the 

 shield, being convinced that it might by this means, be worked through the 

 worst ground, with a certaintv of safetv and success. 



February 14. — The President in the Chair. 



" Description of Mr. Clay's new Process for making Wrought Iron direct 

 from the Ore ; as practised at the Shirva Works, Kirkintilloch, Scotland." 

 By William Neale Clay. 



In this communication, the author first describes the various stages through 

 which the metal passes, between the reduction of the ore and its arriving at 

 the state of malleable iron, by the ordinary mode of manufacture ; and then 

 he explains the process which he has invented, and introduced practically at 

 the Shirva Works. 



By the ordinary system of iron-making, the ores are reduced into the state 

 of carburet of iron, and then, by refining and puddling, the metal is de-car- 

 buretted, thus making it into malleable iron by a number of processes, which 

 are recapitulated : — 



1st. Calcining the ore. 



2nd. Smelting in a furnace, by the aid of blast, either cold or heated, 

 with raw coal, or coke, for fuel, and limestone as a flux. 



3rd. Refining the " pig " into " plate " iron. 



4tb. Puddling, shingling, and rolling, to produce the "rough," "puddled," 

 or No. 1 bars. 



5th. Cutting up, piling, and rolling, to produce " merchant," or No. 2 

 bars. 



6th. A repetition of the same process, to make " best," or No. 3 bars. 



Seeking to diminish the number of manipulations, by the new process a 

 mixture of dry Ulverstone, or other rich iron-ore (Haematite) is ground with 

 about four-tenths of its weight of small coal, so as to pass through a screen 

 of one-eight of an inch mesh. This mixture is placed in a hopper, fixed 

 over a preparatory bed, or oven, attached to a puddling furnace of the or- 

 dinary form. While one charge is being worked and balled, another gradu- 

 ally falls from the hopper, through the crown, upon the preparatory bed, and 

 becomes thoroughly and uniformly heated ; the carburetted hydrogen and 

 carbon of the coal, combining with the oxygen of the ore, advances the de- 

 composition of the mineral, while by the combustion of these gases, the 

 puddling furnace is prevented from being injuriously cooled. One charge 

 being withdrawn, another is brought forward, and in about an hour and a- 

 half the iron is balled, and ready for shingling and rolling. The cinder 

 produced, is superior in quality to that which results from the common 

 system ; it contains from 50 to 55 per cent, of iron, and is free from phos- 

 phoric acid, which frequently exists, and is so injurious, in all the ordinary 

 slags : when re-smelted, it produces as much No. 1 and No. 2 cast-iron, and 

 of as good quality, as the ordinary "black band" ore of Scotland. The 

 cast-iron produced from the slag (amounting to one-third of what was ori- 

 ginally contained in the ore) is mixed with the ore and coal in the puddling 

 furnace; and thus, while nearly all the iron is extracted from the ore, as 

 much wrought iron is produced iu a given time, and at the same cost of fuel, 

 as by the old system. The first process, producing puddled bars of superior 

 quality, is consequently on a par with the fourth stage of the old system, aa 

 it avoids the necessity of the preceding separate manipulations. From the 

 absence of all deleterious mixture, by once piling and reheating the rough 



