involved in the Construction of Artillery. 



395 



The American experiments embrace some excellent results as to resistance to torsion. 

 The following, though not a summary, may serve as an example: — 



Comparative Resistances to Torsion of the three Materials for Cannon. 



The transverse strength of some of these cast-irons was found to be nearly doublet! in 

 passing through only /oh;- renieltings in place of thirteen. 



The torsion bars were about 2 inches diameter, and 15 inches between the points ol 

 twist. 



The experiments recorded, which are very numerous and valuable as to the relations 

 between ultimate tenacity and specific gravity in cast-iron, are quite in accordance with 

 my own former experiments (sections 55, 56, 57), and with the statements of the text; 

 several apparent anomalies, left without explanation in the United States Reports, beinij 

 accounted for by the application to them of the principles advanced by myself. 



The following Table presents, in one view, most of the constants for cast-iron suited for 

 gun-founding, deduced by the American experimenters : — 



Cast-Iron. 



The experiments as to hardness were made by pressing, under a constant load, a rec- 

 tangular, prismatic, sharp steel tool, into the several metals, observing the depth, length. 



