VI. TERRESTRIAL MAGNETISM. 297 



the altitude of the Northern Lights. By means of an instrument designed by 

 the exhibitor, the point of convergence of the uortli light rays is to be 

 accurately determined, as well when at the appearance of the corona it is 

 situated above the horizon, as when it is below the same, and in regard to 

 altitude and azimuth. By the deviation of the point of convergence from the 

 direction of the dipping needle, the height of the north light rays can be 

 calculated. 



1231b. Compass with Diamond Fin. 



Ernst Winter, Hamburg, EimstusteL 



