— 236 



Having in this way investigated the correlative character 

 of diagrams and the inequality of horizontal and vertical 

 components at different stations, it was the natural course of 

 things to stiidy the synchronous system of vectors for different 

 moments diiring one rotation of the earth. 



For this we may i-estrict ourselves to the arctic stations 

 which lie relatively close to each other; besides the original 

 observations at these stations having been taken at the 

 Göttingen hours they are conseiinently trnly synchronous. 



To ühtain a survey of these synchronous systems, 12 niaps 

 of the arctic calote have been constructed in stereographic 

 projection. They are reproduced on the plate. 



