94 



linen-cloth hung up in the air, the v. r. could be seen at 2 

 cm distance. It is clear that the cloth being half transparent 

 did not hinder the light in any noteworthy degree. The 

 line appeared of the same intensity in all directions. 



I order to ascertain if the light was produced by some 

 diffuse reflexion from the snow, we made following experi- 

 ments. An ordinary mirror was put on the snow and the 

 slit directed by turas to the mirror and to the snow but no 

 difference in the intensity of the line could be observed. It 

 is obvious that the light did not come from the snow but 

 that the air between the slite and the mirror or snow was the 

 source of the light. Even on black soil (without snow) this 

 phenomenon was observed; the above mentioned observa- 

 tion (in parenthesis) was made when the soil was without 

 snow. 



There is no doubt that the places of observation were 

 by such occasions situated within the space of an electric 

 air-current, though the prevailing atmospheric circumstances 

 did not permit a light of noteworthy intensity to appear. 

 This space would surely have appeared more light, if it hacl 

 been compared with a totally dark space, where no current 

 existed. The naked eye could not discover the light but in 

 the spectroscope where it was concentrated on a single line, 

 it vas observed with astonishing clearness. That such an 

 observation hitherto has not been made, depends clearly on 

 the fact that a spectroscope has not always been at hand, 

 but most probobly that the idea to direct the instrument to 

 a seemingly dark space has never crossed the mind. 



Goncerning the luminous phenomena, natural and ar- 

 tificial över the point-apparatus, a great number of experi- 

 ments were executed, with following results. 



Luminous phenomena above the point-apparatus appe- 

 ared in many different forms: feeble flames, diffuse light 

 weaker or stronger, ray-formed flames with a moveable 

 lyminous knöt and beams över 100 m in height. 



