710 TERRESTRIAL MAGNETISM, 



readings for an hour to be taken at all three instruments, and in 

 such a way that different hours were chosen in each day. Besides 

 this, we observed in order to obtain an insight into the whole 

 daily proceedings, twice in the month, at interval of 5 minutes 

 through 24 hours. To obtain the observations as nearly as 

 possible at the same exact time, the three instruments whose tele- 

 scopes were all fixed on the same axis, were read off one after 

 another as quickly as possible (on an average within 8 to 10 

 seconds). These observations were continued from the middle of 

 January till the end of April, in all 32 observation-days, and I 

 think that put together they will give a true picture of the con- 

 tinuous changes as regards the direction and intensity of the 

 Magnetic forces in the Arctic regions." 



" In order to confirm the connexion between the aurorae and the 

 action of the needles, a second observer, independently of the 

 others, observed the changes and motion of the aurorae. Absolute 

 determinations of the three constants were made as often as cir- 

 cumstances permitted, to control the Variation instruments. 



" Apart from the Swedish Expedition, whose observations are 

 not yet published, Lieut. Weyprecht points out that his are the 

 first regular and simultaneous observations that were ever made 

 in the Arctic districts. Moreover, he thinks that all former obser- • 

 vations were made with the ordinary heavy needles, and that he 

 was the first to use the light Lamont needles. For observations, 

 however, under such conditions as the normal ones near the pole 

 prove to be, heavy needles are perfectly useless ; even the com- 

 paratively light intensity needle of Lamont's theodolite oscillated 

 so violently, on account of its unproportionally great moment of 

 inertia, and even with moderate disturbances, that the readings 

 became quite illusory. Almost on each magnetic day some dis- 

 turbances were so great that the image of the scale could no 

 longer be brought into the field of the telescopes on account of 

 deflection ; in order to ascertain also these greatest effects, Lieut. 

 Weyprecht constructed an apparatus by which he could measure 

 them at least approximately. He owns that as a matter of 

 course his observations could not possibly be as perfect as those 

 made at home, but thinks that it will be easy to modify Lamont's 

 instruments on the basis of his experience, so that on a future 

 expedition, where there is a greater staff of observers, results could 

 be obtained of any desired exactness. Altogether Lieut. Wey- 

 precht's party of observers, consisting besides himself only of 

 Lieut. Brosch and Ensign Orel, have taken about 30,000 readings 

 from their different magnetic instruments, and the principal results 

 are the following : — 



'' The magnetic disturbances in the district visited are of extra- 

 ordinary frequency and magnitude. They are closely connected 

 with the aurora boreaHs : the quicker and more fitful the motion 

 of the rays of the aurora, and the more intense the prismatic 

 colours, the greater are the magnetic disturbances. Quiet and 

 regular arcs, without changing rays or streamers, exercise almost 

 no influence upon the needles. With all disturbances the declina- 

 tion needle moved towards the east, and the horizontal intensity 

 decreased, while the inclination increased. Movements in an 



