532 BRICK 



According to Posidonius, these bricks were made of a kind of argillaceous earth, which 

 was employed to clean silver plate. But as it could not*be our tripoli, which is too 

 heavy to float in water, M. Fabroni tried several experiments with mineral agaric, 

 guhr, lac-lunae, and fossil meal, which last was found to be the very substance of 

 which ho was in search. This earth is abundant in Tuscany, and is found near Cas- 

 teldelpiano, in the territories of Sienna. According to the analysis of M. Fabroni, it 

 consists of 55 parts of siliceous earth, 15 of magnesia, 14 of water, 12 of alumina, 3 

 of lime, and 1 of iron. It exhales an argillaceous 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 com- 

 posed of this substance, either baked or unbaked, float in water ; and ^th part of clay 

 may bo added to their composition without taking away their property of swimming. 

 These bricks resist water, unite perfectly with lime, are subject to no alteration from 

 heat or cold, and the baked differ from the unbaked only in the sonorous quality which 

 they have acquired from the fire. Their strength is little inferior to that of common 

 bricks, but much greater in proportion to their weight ; for M. Fabroni found that a 

 floating brick, measuring 7 inches in length, 4J in breadth, and 1 inch 8 lines in 

 thickness, weighed only 14j oz., whereas a common brick weighed 5 Ibs. 6| oz. 



As an experiment, M. Fabroni constructed the powder magazine of a ship of these 

 bricks ; the vessel was set on fire, and sank without exploding the powder. 



This earth has been found near Clermont, in the Auvergne. Ehrenberg has shown 

 that it is entirely composed of microscopic siliceous shells. Bricks composed of this 

 earth weigh only half as much as the ordinary ones. 



Fire bricks are made extensively in the neighbourhood of Newcastle-on-Tyne and 

 at Stourbridge. For the analyses of the clays of which these and others are con- 

 structed, see CLAY. 



Stone Bricks. These are manufactured at Neath, in Glamorganshire, and are very 

 much used in the construction of copper furnaces at Swansea. They are usually 

 known as the ' Dinas bricks.' 



The materials of which the bricks are made are brought from a quarry in the 

 neighbourhood. They are very coarse, being subjected to a very rude crushing 

 operation under an edge stone, and, from the size of the pieces, it is impossible to 

 mould by hand. There are three qualities, which are mixed together with a little 

 water, so as to give the mass coherence, and in this state it is compressed by the 

 machine into a mould. The brick which results is treated in the ordinary way, but 

 it resists a much greater heat than the Stourbridgo clay brick, expands more by heat, 

 and does not contract to its original dimensions. The composition of the throe 

 materials is as follows : 



From Pendreyn From Dinaa 



Silica 94-05 100' 91-95 



Alumina, with a trace of ox. iron 4'55 traces 8 '05 



Lime and magnesia .... traces traces 



98-60 100- 100-00 



Dr. Richardson: Knapp's Technology, 



Since the introduction of the Siemens gas-furnace, and the Bessemer process for 

 cast-steel manufacture, into countries which, unlike our own, are not well supplied 

 with fire-resisting materials, great difficulty has been experienced in obtaining 

 bricks of a sufficiently refractory character to withstand the extremely high tempera- 

 ture developed in the melting chamber, as well as the sudden and violent alternations 

 in other parts of the furnace. In order to obviate this difficulty, Mr. Joseph Khern, 

 a well-known Austrian metallurgist, has introduced a plan of manufacturing siliceous 

 bricks, which he describes as being superior to any other refractory material obtained 

 in Austria. The chief ingredient is quartz of the highest possible degree of purity, 

 especial care being taken to reject all such samples as show any admixture of iron 

 or copper pyrites, carbonate of lime, or even mica, or felspar. The quartz so selected 

 is heated in quantities of from 10 to 15 tons, in a Eumford lime-kiln for 10 or 12 

 hours, till it attains a full red heat, when it is quenched in water ; the fragments are 

 then cleaned by a simple jigging process, and subsequently are crushed under a tilt 

 hammer, sufficiently fine to pass through a sieve having 60 holes to the square inch. 

 The hammer weighs 2 cwts., and is capable of crushing 3^ tons of quartz in 12 hours. 

 Two varieties of clay are used, differing slightly in plasticity ; they are prepared by 

 careful weathering, pulverisation under light stamp-heads, and grinding under edge 

 rollers ; a final sifting is performed through a sieve of 600 apertures to the inch. The 

 purest quartz is reserved for the first quality of brick, which Jiave to resist the greatest 



