538 



BRONZE 



copper, or more exactly 100 parts of tin and 215 copper), form the ordinary speculum 

 metal of reflecting telescopes, -which is of all the alloys the whitest, tho most brilliant, 

 tho hardest, and the most brittle, The alloy of 1 part of tin and 10 of copper (or 

 nearly one atom of tho former to eighteen of the latter), is tho strongest of the whole 

 series. 



Ornamental objects of bronze, after being cast, are commonly laid upon rod-hot 

 coals till they take a dull red heat, and are then exposed for some time to tho air. 

 The surface is thereby freed from any greasy matter, some portion of the zinc is dis- 

 sipated, and tho alloy assumes more of a coppery hue, which prepares for tho subse- 

 quent gilding. Tho black tinge which it sometimes gets from the fire may be removed 

 by washing it with a weak acid. It may be made very clean by acting upon it with 

 nitric acid, of specific gravity 1-324, to which a little common salt and soot have been 

 added, the latter being of doubtful utility ; after which it must be well washed in 

 water, and dried with rags or sawdust. 



For the following Table we are indebted to Mr. Eobert Mallet, F.R.S., whoso 

 investigations in this direction have been most extensive, and as accurate as they are 

 extensive : 



Bronze, Phosphorised. By carefully dropping phosphorus on melted bronze or 

 copper a product rich in phosphorus is produced. This alloy is claiming much 

 attention, and will be fully treated of under the head of PHOSPHOR BKONZE AND 

 COPFEE, which see. See also ALUMINIUM BBONZE. 



Bronze Imports are now included under the heads of Brass, Bronze and Metal, 

 Bronzed and Lacquered. Of these articles the following Imports are given in 

 1872: 



Cwts. 



From Germany 679 Value 7,128 



Holland 536 4,718 



Belgium 303 2,317 



France 4,236 44,102 



United States of America . . . 7,848 35,331 



Other countries 3,773 16,179 



Total 



17,375 



109,774 



In the same year the Exportation of the same metals is given as 



To all countries . . . . 1,018 cwts. valued at 5,650. 



1 E signifies earthy ; c c, coarse crystalline ; p C, fine crystalline ; o, conchoidal ; v, vitreous ; v c, 

 vitreous-conchoidal ; T c, tabular crystalline. 

 All these alloys are found occasionally in bells and specula with mixtures of Zn and Pb. 



