53 



Bohnenberger's ' Zeitschrift fur Astronomic,' having an aperture of 

 3 inches, and a focal length of 46 inches, French measure, which 

 bears a power of from 300 to 360 extremely well. The success of 

 this object-glass has induced him to attempt the construction of a 

 similar refractor with an aperture of 54 lines, and a focal length of 

 only 48 inches. 



Professor v. Kobell has announced to the same Academy the dis- 

 covery of a new acid, dianic acid, in the mineral called tantalite, from 

 Tammela, euxenite, seschynite, and samarskite. 



December 20, 1860. 



General SABINE, Treasurer and Vice-President, in the Chair. 

 The following communications were read : 



I. "Notice of recent Scientific Researches carried on abroad." 

 By the FOREIGN SECRETARY. 



On the 29th of last November, an extract was read before the Berlin 

 Academy from a memoir on the magnetization of iron and steel, 

 by Professor Wiedemann. In following up his investigations on the 

 relation between the magnetic and mechanical properties of iron and 

 steel, published in the ' Verhandlungen der Baseler Naturforschenden 

 Gesellschaft,' Band II., Professor Wiedemann has obtained the fol- 

 lowing results : 



1 . If an iron wire be twisted during or even after the passage of a 

 voltaic current through it, the wire becomes magnetic. 



When the wire is twisted in the manner of a right-handed screw, 

 the point at which the current enters becomes a south pole, in the 

 opposite case it becomes a north pole. If, during the passage of the 

 current, the wire be twisted in different directions, the polarity changes 

 with the direction of the twist. If it be twisted in different directions 

 after the interruption of the current, the magnetism produced by the 

 first twisting diminishes rapidly. 



2. If a voltaic current be transmitted through a magnet in the 

 direction of its axis, the magnet will twist. 



The experiments were made with wires of iron and steel, of from 1 to 

 2 millimetres in diameter, surrounded by a voltaic helix, and stretched 



