

BRITTLE SILVER ORE 533 



heafc; while the second and third class, for less exposed positions, are made chiefly of 

 the remains of bricks which have been already used, ground and sifted afresh. The 

 following are the mixtures employed : 



First class : 16 parts of quartz to 1 plastic clay, or 14 parts of quartz to 1 of leaner 

 clay. Second class: 18 parts of ground bricks of the 1st class, to 1 of clay. Third 

 class : 8 parts of ground oricks of the 2nd and 3rd classes, to 1 of clay. 



The latter class are made more with a view to obtain mechanical strength than fire- 

 resisting power. 



The materials are mixed together dry, and are thoroughly incorporated by knead- 

 ing with water, and treading under men's feet; about 18 cubic feet are operated 

 upon at one time. Sufficient water must be added to allow the mixture to be worked 

 into a ball between the fingers without crumbling. The second and third class 

 bricks are formed in open moulds, the stuff being beaten down by a metal rammer of 

 about 4 Ibs. weight ; the first class, however, are subjected to a pressure of about 

 3 tons to the square inch during a period of three quarters of an hour, before they 

 are removed from the moulds. The drying takes place in chambers, through which 

 a current of air passes, at the ordinary temperature in summer, but artificially warmed 

 in winter ; the bricks are fit for burning in from 4 to 6 days. The kilns are rect- 

 angular chambers, each having two step-grate fireplaces in one of the shorter sides, 

 and a flue communicating with a high chimney at the opposite end. The capacity is 

 about 2,300 or 2,500 bricks. As soon as the kiln is filled, the charging aperture is 

 partly closed, and a gentle fire is kept in the grates, the flue damper being shut. 

 After 36 hours, the charging hole is entirely closed, and the draught is urged by 

 opening the damper inch by inch at intervals, until, at the end of 65 or 70 hours, the 

 whole of the charge has attained a strong white heat. The fires are then removed, 

 the damper is shut down, the grates are filled with sand, and any cracks that may 

 have formed in the kiln are carefully luted up. After standing in this way for 24 

 hours, the charging place is gradually opened, and in from 36 to 48 hours more, the 

 burnt bricks may be removed. 



BRICK CLAY. The familiar term for any clay used in the manufacture of 

 bricks. A good clay for this purpose is a silicate of alumina, combined in various 

 proportions with sand. Brick clay is used by geologists in contradistinction to 

 Boulder clay. 



BRICK EARTH. A marly earth, containing much alumina, largely employed 

 in brick-making. 



BRICK KILN. See KILN. 



BRICK Oil.. This is a relic of old pharmacy : it was prepared by putting red- 

 hot roughly powdered brick into linseed oil. It is no longer used, except by old 

 apothecaries and druggists in remote country towns. 



BRICK RED COPPER ORE. See TILE QBE. 



BRIDGE. See IKON BRIDGE. 



BRIMSTONE. (Soufre, Fr. ; Schwefel, Ger.) SULPHUR. 



Our Imports of Brimstone for the years ending 1871 were as follows: 



1869 1870 1871 



Quantity Value Quantity Value Quantity Value 



Cwts. Cwts. Cwts. 



1,015,329 388,723 1,065,360 386,660 937,049 303,717 



BRISTIiE. The stiff glossy hair of swine, which grows chiefly on the backs of 

 those animals, both in the wild and the domesticated state. Bristles are used in the 

 manufacture of brushes. 



In 1864 our Imports of Bristles from Eussia were 1,958,1 12 Ibs., valued at 252,9232.; 

 from Prussia 59,113 Ibs., valued at 7,6352. ; from Hamburg 207,274 Ibs., valued at 

 26,7722.; from Belgium 34,880 Ibs., valued at 4,5052. ; from Prance 51,859 Ibs., 

 valued at 6,6992. ; from other parts 34,897 Ibs., valued at 4,5072. : total amount, 

 2,346,135 Ibs., valued at 303,0412. In the same year we exported 12,395 Ibs. valued 

 at 2,2642. The importations for 1872 were: From Kussia, 1,800,933 Ibs.; from 

 Germany, 572,727 Ibs. ; from Holland, 492,921 Ibs. ; from Belgium, 94,842 Ibs. ; 

 from France, 60,030 Ibs. ; and from other countries, 46,642 Ibs. The total value 

 being 517,8092. 



BRISTOL DIAMONDS. Brilliant crystals of quartz, found in the St. Vincent 

 Kocks, near Bristol. They are often cut and polished for ornaments. 



BRITANNIA METAL. An alloy of tin with copper and antimony, In the 

 best kinds a little nickel is used. See ALLOTS. 



BRITISH GUM. See DEXTBINB. 



BRITTLE SILVER-GLANCE. See SlLVEB ORES. 



BRITTLE SILVER ORE. See SlLVBB OBBS. 



