22 



B. From tie State of Cauca. 



1. Supia district. 



9. Marmato district. 



1 0. Marmato district (in cubes). 



20. Loaisa mine, Marmato district. 



37. Crystallized gold, lode of Pital mine, near Marmato. 



40. Collection of metallic ores from the United States 

 of Colombia, South America. 



1883. Lent by II. ~Blake White. 



41. Set of specimens of coal, ironstone, limestone, and 

 cold blast iron. Illustrating the exact proportions, both 

 in weight and bulk, of the minerals, coal, ironstone, and 

 limestone consumed in the blast furnaces for the pro- 

 duction of one cubic inch of cast iron at the Bowling 

 Ironworks. 



1876. 

 Exhibited by the Howling Iron Company, Limited. 



The coal is coked and the ironstone calcined preparatory to 

 their introduction into the blast furnace. 



42. Specimens of steel, &c. produced by the Basic or 

 Thomas-Gilchrist process. 



1887. Exhibited by Percy Gilchrist, F.R.S. 



43. Microscopical photographs of sections of iron and 

 steel. 



1876. Lent by Dr. H. C. Sorby, F.R.S. 



The above were photographed by means of strong surface 

 illumination, and show structures due to the arrangement of 

 crystals of iron combined with a varying amount of carbon, 

 of portions of slag, and of crystalline plates of graphite. Note 

 the contrast between the structure of cast iron, cast steel, and 

 meteoric iron, although all have solidified from fusion. 



44. Specimens of native iron. 



1876. Lent by George Gore, F.E.S. 



45. Specimens of native antimony. 



1876. Lent by George Gore, F.R.S. 



