170 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



punching hardens is proved by the five-eighths-iuch and one-half-inch 

 plates only stretching l.'J and 3.2 per cent., and also by their break- 

 ing very suddenly, as attested by the appearance of the fracture, one 

 being wholly and the other within 5 per cent, of wholly granular, 

 whereas the others are wholly silky. Heating and annealing the speci- 

 mens after being punched is found to counteract to a considerable ex- 

 tent the injurious action, the loss in the liveeighths-iuch being reduced 

 from -19.04 to 31.32, aud the one-half-inch from. 45.17 to 30.12, and in- 

 stead of extending 1.9 rose to 20.7, and from 3.2 to 19.3 per cent., and 

 the appearances of the fractures from wholly granular to wholly silky 

 in the one, and from 95 per cent, granular to wholly silky in the other. 

 The mean loss of the five annealed is 31.63 and 37.85 in the uuannealed, 

 their joint average being 34.74 per cent. This average loss, however, 

 would have beeu much greater had the material not been so extremely 

 soft and ductile. 



Series G. 



The effects of bulging stress on rolled steel plates of various thick- 

 nesses was tested upon the same material as series D, E, and F. 



The specimens for the above test were disks, 12 inches in diameter, cut 

 out in a lathe, and pressed through an aperture 10 inches in diameter, 

 the end of the plunger being turned to a radius of 5 inches. The two 

 woodcuts which accompany the tabulated rei)ort of the results, series 

 G, show the form of the specimen previous to and after experiment. 

 Ten pieces were tested as rolled, uuannealed, and ten after being annealed. 



The following stresses were required to force the specimens of the 

 various thicknesses through the aperture : 



Thickness. 



Pounds. Pounds, j Pounds. Pounds. Pounds. 



Unannealed 215,685 162, 735 j 104,845, 71,800 35,397 



Annealed ..i 198,005] 154, 2o0 I 95,605 59,425 25,435 



All the specimens stood the ordeal without the slightest sign of any 

 crack or defect in the manufacture. The clear tone given out, on being 

 struck, by all the specimens after being bulged, excepting those that 

 buckled owing to their thinness, proves the soundness of the material. 



MANGANESE. 



Manganese Ore. 



The ores of manganese consist of various oxides of manganese, both 

 hydrous and anhydrous, and find application for two distinct purposes, 

 bleaching and steel-making. For bleaching purposes the manganese 

 ore is dissolved in hydrochloric acid which gives off free chlorine that 



