354 Mr. J. Napier on Cupper Smelthig. 



regards heat, docs not make a good bottom for furnaces where 

 copper is to come into contact with it. The following were found 

 quite unsuitable :- 



99-G4 100-0 



Alumina seems to be the deleterious ingredient in this sand, 

 and confirms our remarks in reference to fire-bricks and clay. 

 And this is fully borne oiit where sand with alumina is found 

 uncombiued and capable of being separated by washing, as in 

 some parts of Australia. 



Sand as dug up, unsuitable for bottoms, not lasting more than 

 ten or twelve days : — 



(A. D. Thomas.) 

 Silica .... 85-18 

 Alumina . . . 9-10 

 Oxide of iron . . 3-00 

 Lime .... 1-12 

 Magnesia . . . 1-60 



100-00 



This being washed in a small running stream, gave a sand" which 

 lasted as bottoms from six to eight weel\s. Analysis gave — 



Sihca 92-0 



Carbonate of lime . . . 5*6 



Carbonate of magnesia . 1-6 



Oxide of iron and alumina -8 



100-0 



It is worthy of remark how a slight difference in the per-centage 

 of silica will effect the fusibility — the tear and wear of a bottom. 



We are not aware that the Isle of Wight or American sands 

 used in making crystal have been tried for bottoms. As they 

 contain upwards of 99^ per cent, of silica, the bottoms would 

 probably prove very lasting ; but there might be some danger of 

 a liability to crack owing to the fineness of the grain. 



Roofs of furnaces and lining of stacks or culverts near the fur- 

 nace arc often affected by the volatilized matters passing over 

 them ; those from the calciner are not so destructive to the bricks, 

 the heat not being so intense as to cause combination. The 

 volatile matters only condense and form a deposit or crust upon 



