478 



BRICK. 



grooves should be radii of the circle, of which the in- 

 tended arch is a segment. It is, however, recom- 

 mended, that if the arch be particularly flat, or appli- 

 ed in situations which do not admit of end walls, to 

 have the shoulders dove-tailed, to prevent the arch 

 cracking across, or giving way edgewise. In form- 

 ing an arch, the bricks must be coursed across the 

 centre, and a grooved side of the bricks must face the 

 workmen. The bricks may be either laid in mortar, 

 or dry, and the interstices afterwards filled up by 

 pouring in lime-putty, Paris plaster, or any other 

 convenient material. The obvious advantages of 

 arches constructed upon this principle, are, that 

 the same centre, which, whatever be the breadth 

 of the arch, may be in no case many feet wide, may 

 be regularly shifted as the work proceeds ; and as they 

 have no lateral pressure, they require no abutments 

 to prevent their expanding at the foot, nor any 

 weight upon the crown to prevent their springing 

 up. They may be laid upon a common perpendicu- 

 lar wall, and if used in the construction of common 

 buildings, they will not only preclude the necessity, 

 and save the expence of timber, but will also afford 

 an absolute security against the possibility of fire. 

 A new invention in the formation of bricks, by M. 

 Legressier, has lately been announced in the Arc/lives 

 lies Decoirvcrtes ct Acs Inventions Nouvclles, pendant 

 1'annee 1809. The principle, however, is merely 

 that of Mr Cartwright'e, followed out to a greater 

 extent than has perhaps ever been done in this coun- 

 try. M. Legressier proposes, that the bricks should 

 be formed in seven different moulds, according as they 

 are to be placed in the middle or on the exterior of 

 the walls ; in the bottom or on the top ; in the arches 

 or in the corners ; a/id by the proper disposition of 

 these bricks in the building, every pressure, either 

 longitudinally or laterally, is resisted, in proportion 

 to the strength of the indentures by which they are 

 locked together. But as our limits will not admit 

 of a detailed account of this supposed new invention, 

 we shall present the reader with the original article.* 



Besides the place bricks, and grey and red stocks, 

 which are used in common building, there are marie 

 facing bricks, cutting bricks, fire bricks, and floating 

 bricks. The first of these are of a fine yellow colour, 

 hard and well burnt ; they are made in the neighbour- 

 hood of London, and are used in the outside of build- 

 ings. The cutting bricks are made of the finest kind 

 of marie ; and, as we have already observed, are em- 

 ployed iu the construction of arches over windowi 

 and doors. Fire bricks, sometimes called Windsor 

 bricks, because an excellent kind of them are made 

 at Hedgesley, a village near Windsor. They con- 

 tain a large proportion of sand, and will stand the 

 utmost fury of fire, and are consequently used for 

 coating furnaces, and lining the ovens of glass- 

 houses. Clay for fire bricks is got at most great 

 collieries, but particularly at Stourbridge, which pro- 

 duces the best clay for this purpose in England. 

 Floating bricks are a very ancient invention : they 

 are so light as to swim in water ; and Pliny tells us, 

 that they were made at Marseilles, at Colento in 

 Spain, and at Pitane in Asia.f This invention, 

 however, was completely lost, until M. Fabbroni, 

 published a discovery of a method to imitate the 

 floating bricks of the ancients. \ According to Posi- 

 donius, these bricks were made of a kind of argil- 

 laceous earth, which was employed to clean silver 

 plate. But as it could not be our tripoli, which ij 

 too heavy to float in water, M. Fabbroni tried seve- 

 ral experiments with mineral agaric, guhr, lac-lunse, 

 and fossil meal, which last was found to be the very 

 substance of which he was in search, This earth is 

 abundant in Tuscany, and is found near Casteldel- 

 piano, in the territories of Sienna. According to the 

 analysis of M. Fabbroni, it consists of 55 parts of 

 siliceous earth, 15 of magnesia, 14 of water, 12 of 

 argil, 3 of lime, and one of iron. It exhales an argil- 

 laceous odour, and when sprinkled with water, throws 

 out a light whitish smoke. It is infusible in the fire, 

 and though it loses about an eighth part of its weight, 

 its bulk is scarcely diminished. Bricks composed of 



* " M. Legressier a pcnsd qu'on pouTrait perfeetionner la fabrication des briques en leur dormant line forme pnrticuliere. 

 II propose des briques a enclaves composers d'unc enclave principnlc, et donnant sept moules diffcrens, y compris les encoig- 

 nures, les cintres et les plans circulaires. Ces enclaves forment les parties saillantes, et les entailles les parties rentrantes ; 

 Tune et 1'autre sont a queue d'aronde ou a biscaux. Les divisions et les oppositions des enclaves et des entailles sont les memes, 

 et correspondent ensemble; la coupe en diffre, en ce que les angles sont aigus sur les faces laterales pour former les queues 

 d'aronde, tandis qu'ils son droits sur les faces d'assisea, afin d'efl'rirles enclaves a biseaux. 



Dans le systeme de 1'auteur, il y a des briques de plusieurs formes, suivant qu'elles doivent etre placees au milieu de la ma- 

 ^onnerie, en premier lit, en dernier lit, sur les faces exterieures des murs, aux angles ou dans les parties courbes. 



Lorsque ces briques doivent etre placees au milieu des murs, elles ont des parties saillantes et rentrantes sur leurs six faces; 

 savoir, quatre a queue d'aronde sur les faces laterales, et deux a angles droits sur les parties inferieure et superieure. Lorsquc 

 elles sont destinees a etre en premier lit, en dernier lit, ou dispos&s sur les faces exterieures des murs, les parties saillantes on 



. lateralement, proportionnelle a la force des queues d'aronde. 



L'auteur assure que ces briques s'opposent aux pousse'es, et previennent meme les ecartemens ; qu'elles ne peuvent permet- 

 tre le tassement que d'une maniere egalc sur tons les points d'unc fondation ; qu'elles procurent Economic de matiere pour les 

 pierres de taille et moellons, economic de temps pour les transport et la taille de ces pierres, et enfin que la re'gularite de la 

 jonction de ces briques dispense presque de se servir de plomb et de cordeau pour les poser. 



Ces briques etaut fabrique'es dans des nnoules en metal auront line precision parfaite qui ne permettra pas de les confondre, 

 et nc sera pas altered par le ciment ; car on nc devra se servir pour les re'unir que de chaux vive re'duite a la consistance d'une 

 bouillie." 



f- Nat. Hist lib. xxxv. cap. 14. 



This small work consists only of 24 octavo pages, and was published at Venice, under the following title : Di una 

 golariusima specie di mattoni ossia ritravnmento degli anticki mattoni gallegianti, diaertazione tetta. nelltt. pubtica adunanta act 

 fieorgofili de Fircnse, fanito 1791, dal Signer Fabbroni. 



