482 THE POPULAR SCIENCE MONTHLY. 



tint, lightly washed with green, was shown. Although the meteor 

 was not visible continuously, there was often observed in the spectro- 

 scope, and even quite high above the horizon, the characteristic band of 

 the auroras without the eye perceiving any trace of their light. Since 

 this fact was remarked even when there was no snow, it could not be 

 attributed to reflected auroral flashes. Moreover, the observers not 

 rarely saw during the nights a light yellowish, diffuse, and phosphores- 

 cent light that illuminated the horizon and paled the stars. The effect 

 produced was compared to that of the moon half veiled by clouds. M. 

 Lenstrom and his associates attempted, on the 8th of December, 1882, 

 to measure the height of an auroral arc above the surface of the earth. 

 They divided themselves into two groups, and took with a theodolite the 

 angular distance from the crest of the arc to the horizon. The two sta- 

 tions were four and a half kilometres apart on the same magnetic me- 

 ridian, and correspondence was had during the observations by a tele- 

 graphic wire previously arranged for the purpose. They endeavored to 

 look in concert at the same point of the meteor, but, after reiterated es- 

 says, they recognized that any particular ray visible to one party could 

 not be seen by the other. The results of the views were irreconcilable, 

 for the angle obtained was greater for the southern post than for the 

 northern one, although the latter post was, a priori ', nearer to the me- 

 teor. M. Lenstrom concluded from this, as M. de La Rive had done, 

 that every observer sees his own aurora the same as every one sees his 

 own rainbow, and that the phenomenon is produced at the height of only 

 a few thousand metres. He also calls attention to the results obtained 

 in Greenland by the engineer Fritze, which lead, in certain cases at 

 least, to numbers twenty times as small. During the Swedish Polar 

 Expedition of 1868, faint flashes or phosphorescent lights were remarked 

 around the summits of the mountains. This fact, with which M. Len- 

 strom did not become acquainted till 1871, related as it was to some of 

 the descriptions given by other travelers, decided him to try to pro- 

 voke or facilitate the appearance of the meteor by artificial means. 

 The first attempts date from 1871, and, like those that followed them, 

 were made in Lapland. The enterprise being successful from the first, 

 the experiments were resumed' during the Finnish Polar Expedition 

 of 1882, and were renewed twice on two different peaks, called re- 

 spectively Oratunturi and Pietarintunturi. Oratunturi, rising more 

 than five hundred metres above the level of the sea, is situated in lati- 

 tude 67 21', near the village of Sodankyla. Near the topmost height 

 of the mountain was placed a long copper wire, 60 bent upon itself as 

 to form a series of squares within squares, having a total surface of 

 nine hundred square metres, supported by insulated posts. Tin points 

 or nibs bristled out from this connecting net at distances of half a 

 metre apart, and the whole was connected by an insulated wire running 

 along on stakes with a galvanometer fixed in a cabin at the foot of the 

 peak. The galvanometer was connected with the earth by the other ex- 



