BRICKS. 



BRICKS. 



IN 



Common brick* are mad* from the coarser description* of clay*, and 

 UM Uur art generally ao stiff a* to require to b* mixed with certain 

 proportions of and, or of ooal aahaa, to enaure their plasticity. The 

 day is dug, and exposed to the weather in amall piece., called, near 

 London, nrfi. in order, at the workman *ay , " to mellow," and it a then 

 mixed with the mad or aahe* in aoch a manner aa to enaure the equal 

 distribution of thoae ingredient*. Thia operation u called tailing, and 

 it ia succeeded by the tempering, which U effected by turning over the 

 clay by hand, and aubaequently by passing it through the pug-mill, 

 previously to Ha being carried to the moulder'* (tool. It U true that 

 moat of then operation! are required to be performed in the prepara- 

 tion of all kind* of brick* ; but the preparation and previous manipu- 

 lation of Minium clay* require to be effected with more care than ia 

 neeeaiary with the clay* of a superior quality. 



The common brick* are invariably burnt in clamps in England and 

 in Belgium. In England the products are classed, according to their 

 quality, either as cuttm, or the fine grained rather soft bricks used 

 for cutting ornamental work ; picl-al itucla, of a bright uniform colour ; 

 sjnmn, or the hardest and moat regular bricks, fitted for the purpose 

 indicated by their name ; common ttaela, griabi, turn or attain?. 

 Many of these names are applied to the differently coloured brick* 

 before referred to, and it may suffice here to say that the red, blue, or 

 black colour* in question result from the variable proportion* of tlie 

 hydrous oxide of iron in the days, and they change as the clays them- 

 selves may be affected by the degree of heat to which the bricks are 



Paving brifit are made from clay* containing silica, in a form 

 which would allow of its passing into a state of semi-fusion, and thus 

 of producing a hard imperishable material The best paving bricks 

 are made from the mud of the Yssel in the Netherlands, and they are 

 known in commerce under the name of Dutch clinker* ; very good 

 materials of this description are, however, made at Uppingham from the 

 clays of the lower oolite ; or in the neighbourhood of Birmingham, 

 from the days of the carboniferous series. 



Fire briett are those which are used in positions where they are 

 required to resist the direct action of fire, and they must, therefore, 

 be of an infusible nature. This term is, however, only to be used 

 relatively ; that is to say, it must be understood that the danger of 

 fusibility will vary in every different description of furnace, and the 

 brick* required to resist the heat of an engine furnace will be exposed 

 to a heat which will be far less than that of a porcelain kiln. What- 

 ever be the degree of heat to be resisted, the general characteristics of 

 the clay fitted for fire-bricks are that it should be as free as possible 

 from any mixture of lime, magnesia, or iron ; and that the silica should 

 be present in the soluble form. The best fire-bricks are made at 

 Stourbridge, but articles of nearly equal value are made at Edinburgh, 

 Newcastle, Glasgow, South Wales, and latterly the peculiar beds of the 

 subcreUccous formation* near Farnham, in Surrey, have been worked 

 for the purpose of making fire goods of a very peculiar nature. Great 

 pains are required to be taken in preparing the clay for fire-bricks, in 

 order to avoid any unequal contractions or expansions ; and it is essen- 

 tial that the bricks should b* exposed, whilst in the kirns, to a greater 



The dimension* of bricks vary, a* was said before, not only on 

 account of the quality of the clay from which they are made, but also 

 in many cases on account of the fiscal or excise laws of the locality. 

 Upon the Continent bricks are usually made about 8} inches in length, 

 by 4( inches wide, and 2+ inches thick ; but in consequence of the old 

 excise laws of our own country the dimension* of English bricks are 

 ataiost irnvkbljT 9 inches hi length, by 44 inches wide, and 1J e inches 

 M iDciiwt Romans, and even the modern Italians, have 

 adopted <nrj different dimension* from either of the above ; for in 

 their building* brick* are occasionally to be found having a length of 

 MiMhs*). by a width of inches, and . thickness of 2f inches; and in 

 tb old Roman wall of London itself the bricks wen 174 * 11| x 11. 

 Th Ad.tris.1 bricks are often 12x6x24; * old Jtoum bricks of 

 ^ > 18 81; wWrt the ordinary Dutch waul 

 l|. In fact, every imaginable proportion and dimen- 

 ZZL**?***'' bnt ** ""ofr-wMch l>t to regulate 

 them are, nrstiy, that they should not be soch a* to interfere with the 



vper degree of burning; and, secondly, that they should be such as 

 that working man could easily handle the bricks without undue 

 faUgu.; consistently with these condition*, the larger the bricks are. 



the better and more economical will they be, both la manufacture and 

 in use. 



In laying brick*, the most important precaution* to be observed are, 

 that the oemcntitious material should be equally and carefully upph. -1, 

 and that the joint* of the bricks should never be immediately over one 

 another; or, to use the workmen* phrase, the brick* " mu*t break 

 bond." There are two description* of bond commonly adopted in 

 England, which are known under the respective name* of the J-'lemuk 

 and the En'iluk bond, about the relative merits of which there is a 

 great diversity of opinion. The Flemish bond is made by laying the 

 bricks in a course, alternately lengthwise or across the line of the wall, 

 as stretcher* and header* ; the English bond is made by laying all the 

 bricks in one course a* headers, and all those of the course imme- 

 diately above it a* stretchers ; but in both cases care is taken that no 

 vertical joint shall be carried through two consecutive course*, and 

 that the face of the wall shall be carried up vertically, or in regular 

 batter, when the face is not perpendicular. The Urge bricks 01 tin; 

 Romans were, however, used under rather different conditions from 

 those prevailing in modern buildings; for they were in fact used aa 

 bonding-courses in the midst of a large body of rubble masonry, in tho 

 majority of cases, and therefore they did not require the same minute 

 attention to the arrangement of the joints which is necessary whi-n the 

 mass of a wall is composed solely of small, regular-shaped materials. 

 When the Romans used bricks exclusively, they seem to have adopted 

 rather what we should call the old English, than the Flemish bond. 

 In many of the Roman brick arches, bricks radiating to the centre 

 have been used ; and indeed that wonderful people was evidently as 

 well acquainted with the art of making moulded earthenware as are the 

 best manufacturers of our own days. It would appear, also, that their 

 engineers were aware of the fact that the strength of brickwork 

 depends more upon the mortar used in its preparation, than it doe* 

 upon the resistance of the bricks themselves ; for they paid great 

 attention to the composition and to the manipulation of their mortars, 

 aa we shall have occasion to remark in detail, in the articles CEMENT, 

 LIME. In the middle ages, it may be added, the use of bricks took 

 place under nearly the same conditions as in earlier periods, so far aa 

 the mode of placing them in the work is concerned ; but the architects 

 of Northern Italy and Germany obtained new and striking effects of 

 colour by the use of moulded and glazed bricks ; whilst in France and 

 in parts of England architectural decorations were obtained by cutting 

 the brick* themselves. The bricks which admitted this treatment 

 were of course the fine grained, uniform, and rather soft bricks ; but 

 when proper precautions have been observed in placing them, time and 

 exposure have produced far less effect upon their surfaces than might 

 have been expected. 



As the quality of bricks varies within so wide a range, and, as wo 

 said before, the quality of the cemeutitious material used with them 

 limits the practical strength of this description of work, it may be 

 dangerous to attempt to lay down any absolute rules with respect to 

 the resistance brickwork can offer. Mr. Edwin Clark, however, in the 

 course of his experiments at the Henai Tubular Bridge, ascertained 

 that the average resistance of brick-work, set in Roman cement, to an 

 inttanlantoiu effort of compression, was equal to about 83'5 tons upon 

 the superficial foot ; and in the great St. Rollox chimney, near Glas- 

 gow, the weight actually brought upon the lower courses of brick-work 

 is nearly 16 ton* 14 cwt. per foot. In the trials to which some of the 

 brick viaducts of the Havre and Rouen line of railway were exposed, 

 after the fall of the Barentin Viaduct, the crushing weight thrown upon 

 the piers of brick-work, set in ordinary chalk-lime mortar, was made 

 equal to about 6-4 tons on the superficial foot ; but at the time this 

 trial was thought to be exaggerated, even though no accident ensued 

 from it. M. Vicat carried on, some yean since, a aeries of experiments 

 on the subject of the strength of brick- work ; and from them it would 

 appear, that the instantaneous and the safe permanent resistances, per 

 superficial inch, according to the nature of the mortar employed, may 

 be considered to be as follows : 



Itwtantaneous. Permanent. 



Chalk lime and common sand, fourteen years old . 270 lb*. 81 lb>. 



Ordinary hydraulic lime . 1050 315 



Eminently hydraulic lima . 2043 613 



These values are high ; but if care be taken in the execution of the 

 work, they may be adopted as maxima. SI. Vicat also made experi- 

 ment* upon the resistance of similar materials to an effort of extension, 

 and he deduced from them the following table : 



Chalk time and common rand, as before 

 Ordinary bydraulic lime . 

 Eminently hydraulic . . . 



Itutantentoni. Permanent. 

 . 57 lli'. 17 Ibs. 



. 129 39 



*I3 4 



The resistance to an effort of torsion lit usually considered to be equal 

 to about | of the resistance to compression. 



A very important practical observation, with respect to the use of 

 bricks in foundation works, is, that the under-burnt bricks are more 

 easily acted npon by external agent*, such u water containing carbonic 

 acid gas in solution, than are either the unbtirnt clay or the thoroughly 

 burnt brick*. It follows, therefore, that in such positions only the 

 hardest and most perfectly burnt bricks should be used, especially if 



