426 Prof. E. Edlund o?i Atmospheric Electricity 



the air. MM. Lottin and Bravais, who made during the 

 summer experiments of this kind in lower latitudes, obtained 

 positive deflections upon a straw electroscope when it was 

 placed in metallic connexion with arrows shot into the air. 

 Now those deflections ceased to be obtained as soon as the 

 latitude of the North Cape w T as reached. In February and 

 March, however, they several times succeeded in detecting 

 feeble traces of positive electricity in the air on putting the 

 electroscope in connexion with kites which they raised to a 

 considerable height*. During the Swedish expedition to 

 Spitsbergen in 1868, M. Lemstrom tried in vain to discover 

 traces of electricity in the air (80° N. lat.)f. M. Wijkander 

 had better luck in the expedition of 1872-73 to the same re- 

 gions. Furnished with a more sensitive apparatus than those 

 employed by his predecessors, in the autumn of 1872 he con- 

 tinually obtained proofs of positive electricity in the air. 

 During the winter, from the middle of January to near the 

 end of May, on the other hand, the electricity shown was 

 sometimes positive, sometimes negative. In fact he obtained 

 20 positive and about an equal number of negative observa- 

 tions. The observations made in the course of the spring, 

 when the temperature approached zero, gave the same results 

 as the summer observations — namely, slight traces of positive 

 electricity. It is, moreover, a remarkable fact that the air 

 was generally positive during the winter days when aurorae 

 boreales appeared, but on other occasions most frequently ne- 

 gative. Respecting this the following remark is made by M. 

 Wijkander, which in my opinion is well worthy of considera- 

 tion : — "All the observations which were made agree in this, 

 that, in the latitudes in question, at the highest temperatures 

 the air conducts electricity with great facility — a circumstance 

 to which have been attributed the absence of thunder and the 

 presence of the aurora borealis. Divers physicists have be- 

 lieved that this may be assumed to depend on the humidity of 

 the air in those regions ; but that other causes also contribute 

 to it is proved by the fact that the same temperature and the same 

 degree of humidity do not exert this action to so high a degree in 

 lower latitudes y " '{. 



These observations prove indubitably that the cause to which 

 the positive electricity of the air in those regions is due is 

 very feeble. It cannot, in my opinion, be attributed to the 

 humidity and consequent conductivity of the air. If that 



* Voyage en Scandinavie et en Laponie : Magnet, terr., t. iii. ; and verbal 

 communications from M. Siljestrom, who took part in this expedition. 

 t Oversigt af Kongl. Vetemkaps-Akademiens Fdrhandlingar, 1869. 

 j Ofversigt, 1874. 



