286 SEC. 9. MAGNETISM. 



/' 



raised to a white heat a corresponding expansion at a red heat was found by 

 Prof. Barrett, who also discovered that at this moment a crepitating sound 

 was emitted, the wire resumed its magnetic state at this period, and further- 

 more, a sudden reglowing of the wire takes place. These phenomena at this 

 critical temperature are also associated with changes in the conductivity and 

 thermo-electric property of the wire, as discovered by Prof. Tait. See Phil. 

 Mag. Dec. 1873, Jan. 1874, and Report Brit. Ass., 1875, p. 259. 



1136b. Apparatus designed by G. Gore, F.R.S., far exhi- 

 biting the effects of stress upon the magnetisation of iron. 



Prof. IV. F. Barrett. 



1136c. Gore's Apparatus for exhibiting the torsion of an 

 iron wire produced by axial and transverse magnetisation. 



Prof. W. F. Barrett. 



1136d. Apparatus and Diagrams, to illustrate the elonga- 

 tion of unstrained iron produced by magnetisation. 



Prof. W. F. Barrett. 



1137. Coulomb's Torsion Balance for magnetic and electric 

 observations. Warmbrunn, Quilitz. and Co., Berlin. 



1137a. Electro-Magnetic Helix, on wooden tube. Used 

 in electro-torsion experiments. George Gore, F.R.S. 



1137b. Two Wooden Tubes, upon which to form electro- 

 magnetic helices for electro-torsion experiments. 



George Gore, F.R.S. 



1138. Apparatus for the demonstration of Magnetic 



Friction, constructed by the late M. Kleemann in Halle. 



Prof. Dr. Dove, Berlin. 



V.-APPARATUS FOE INVESTIGATIONS CONNECTED 

 WITH DIAMAGNETISM. 



1139. Glass Tubes prepared by Faraday for testing the 

 magnetic and diamagnetic character of Gases. 



The Royal Institution of Great Britain. 



The tubes containing the gas to be examined were suspended in the mag- 

 netic field of a powerful magnet, the result being either attraction or repul- 

 sion of the tubes as the gases they contained were either magnetic or dia- 

 maguetic. Phil. Trans,, 1850. 



1 140. Bars of Borate of Lead Glass, made and used by 

 Faraday, for the action of magnets on polarized light. 



The Royal Institution of Great Britain. 

 Phil. Trans., 1845, 



