38 TEMPERED STEEL CUT. 



smooth edge of the plate remained cool and but 

 slightly abraded. 1 



1 An account of this experiment was published in 1851, in the " Phi- 

 losophy of the Mechanics of Nature," p. 310 ; and recently this experi- 

 ment has been repeated by Mr. Isaac Reese, of Pittsburgh, Penn. An 

 account of the extraordinary results was given by Professor Hendrick 

 to the American Association for the Advancement of Science, in the 

 year 1875. Mr. Reese used a circular disc of malleable iron of the diam- 

 eter of forty-two inches, and with a velocity of the circumference nearly 

 five miles per minute. As stated: " Steel bars, hardened and polished, 

 of the diameter of two or three inches, may be cut off simply by the 

 overpowering excitation induced by the swift rotation of a thin circular 

 disc of soft sheet-iron. The best steel was rapidly cut through. Sparks 

 in a steady stream were thrown off, and particles of steel were found 

 melted together in a conical shape beneath the machine. While this 

 fusion of the steel takes place, the disc itself remains but little heated." 



The powerful excitation induced by the rotation of one%ody near an- 

 other in this experiment, shows the superiority of this method of devel- 

 oping electric excitation to that of Voltaic batteries employed to render 

 a small wire red hot. The velocity of the equatorial surface of the 

 earth, continually rotated opposite the body of the sun, is nearly four- 

 fold swifter than that of the rim of the rotated plate used in the experi- 

 ment of Mr. Reese. 



