84 



SCIENCE. 



[Vol. II., No. 24. 



As long ago as 1871 an attempt was made to assist 

 the production of the aurora upon these hilltops; but 

 the results obtained were not, to scientific men in 

 general, entirely satisfactory. Accordingly, in 18S2, 

 Prof. Lemstrom prepared to repeat his experiments 

 upon a more extended scale. 



Upon the top of Oratunturi Mountain (lat., 67° 21'; 

 long., 27° 17'..3 east of Greenwich), about 540 meters 

 above sea-level, he laid out, upon insulators raised 

 about 2+ m. above the ground, a bare copper wire 

 in the form shown in the illustration, the wires 

 being about 1.5 m. apart. The area covered in this 

 Avay was about 900 square metres. The single wire 

 which made up this spiral was provided with numer- 

 ous points soldered on; and the inner end was con- 

 nected by an insulated line with the observing-station 

 at the foot of the mountain, where the circuit ran 

 through a galvanometer and into the earth. 



ARRANGEMENT OF WIRES. 



From the day the apparatus was finished, viz., Dec. 

 5, " there appeared almost every night a yellowish- 

 white luminosity around the summit of the moun- 

 tain, while no such luminosity was seen around 

 any one of the others! The flames were variable in 

 intensity, and in constant oscillation as those of a 

 liquid fire. Three times it was tested, 2J- miles off in 

 south-east, by a Wrede spectroscope (small size with 

 two prisms), and it returned a faintly continuous 

 spectrum from D to F, in which the auroral line 

 A = 5569 with soft variable intensity was observed." 

 The galvanometer, meanwhile, showed an extremely 

 variable positive current from the wire at the top of 

 the mountain to the earth. 



An attempt was made to determine approximately 

 the electromotive force of this current by occasionally 

 Introducing into the circuit a Leclancb^ element, and 

 observing the change thus produced. As the insula- 

 tion of the line leading up the mountain was not 

 good, however, we must accept with caution, as Pi'of. 

 Lemstrom admits, the results thus obtained. The 

 current from the mountain top was apparently some- 

 times less, and sometimes considerably greater, than 

 the LeclanchS element produced. 



Similar results were obtained at Pietarintunturl 



Mountain (950 metres above the sea, in lat., OS"* 

 32'.5; long., 27° 17'.3 east of Greenwich), where a 

 smaller spread of wire was used. 



There seems to be very little doubt that Prof. Lem- 

 strom has succeeded in producing the aurora at will, 

 or rather in assisting nature to produce it. Some of 

 the conclusions which he draws from his experiments, 

 however, will, no doubt, be received with caution, 

 not because they set forth any thing in itself improb- 

 able, but because the experiments described seem too 

 few and rough to decide the matter beyond a doubt. 

 Thus he believes that " the electricity which descends 

 into the. auroral belt [the circumpolar belt of maxi- 

 mum auroral activity] is the primmnj cause of the 

 greatest part of the terrestrial current, and, through 

 this, of the variations of the magnetic elements." 

 Moreover, finding that in several cases observers in 

 different stations were near mistaking different auro- 

 ral arcs for the same one, he concludes that " all meas- 

 urements of the height of the aurora, calculated on 

 those with a long base north and south, are always 

 erroneous, as the two observers never see the same 

 aurora. And even those calculations which are based 

 on the measurements of the height and length of an 

 arc from one point, and the hypothesis that the arc 

 extends around the magnetic pole, must be consid- 

 ered very unreliable, as no satisfactory answer can 

 be given as to what results would have been obtained 

 a little farther north or south. This is also the case 

 with aurorae with long bases east and west," etc. 

 He says, therefore, "That the height of the aurora 

 borealis is very variable I fully admit, but in my 

 opinion it has been greatly over-estimated." 



It seems probable that a great many people incline 

 to a similar opinion,' and will merely regret that Prof. 

 Lemstrom has not given them some better founda- 

 tion for their disbelief. For many years, however, 

 the doctrine has been current that auroras frequently 

 exist at a height of a hundred miles or more; and the 

 substance of Prof. Lemstrom's present arguments 

 against such a belief must have been old for a long 

 time.'* 



On several occasions it was observed by Prof. Lem- 

 strom's party that the peculiar spectroscopic auro- 

 ral line " was returned from every quarter of the 

 horizontal plane, (and) even from the zenith, withuut 

 any aurora being visible." 



Another phenomenon of much interest is a " pecul- 

 iar phosphorescent 'shine,' or diffused luminosity, 

 which possesses several phases, but the general char- 

 acter of which is a luminosity of a yellow-white 

 color, which renders the night as light as the moon 

 with a thick hazy air." On one occasion "every 

 object around stood out clearly in a yellow-white 

 hazy phosphorescent luminosity of quickly-shifting 

 intensity." Apparently no spectroscope was at hand 

 at this time; but on another in'ght, when a similar 

 'shine,' less bright, but still sufficient to nearly ob- 

 scure the stars upon the horizon, was seen, an at- 

 tempt to discover the auroral line was unsuccessful. 

 It is true that the spectroscope used wasj'not , well 



' Proc. roy. soc, 1879-80, xxx. 332. 

 2 Amer, joiini. ac, xxxix. 286. 



