726 THE AUKORA BOEEALIS. 



Conclusions. — 1. The Aurora Borealis always presents itself 

 in definite and very curious relations to the lines of magnetism, 

 indicated by the needle. 



2. The streamers in the direction of their length coincide with 

 the plane of the dip of the needle or nearly so, and that each 

 individual streamer is, in fact, parallel to the dipping needle. 



3. They form a thin fringe, stretching often a great way 

 from E. to W., at right angles to the magnetic meridian. 



4. The fringe moves away from N. magnetic pole, by the ex- 

 tinction of streamers at its northern face, and the formation of new 

 ones contiguous to its southern face. 



5. The invariable regularity of its appearance, as seen by so 

 many observers, when it comes fully within command of the eye, 

 near the zenith, shows the apparent irregularities, when it is seen 

 either more northerly or southerly, to be only optical illusions. 



6. The region which it occupies is above and contiguous to 

 that of the clouds, or that in which they are about to form. 



14. On the Origin of Atmospheric Electricity, by J. Bec- 

 QUEREL, Senr., reviewed by M. i>e la Rive. (Archives des 

 Sciences, No. 41, 1871.) 



According to M. Becquerei, Solar spots, which are sometimes 

 16,000 leagues in extent, appear to be cavities by which hydrogen 

 and various substances escape from the Sun's photosphere. But 

 hydrogen, which appears here to be only the result of decom- 

 position, takes with it positive electricity, which spreads into 

 planetary space even lo the earth's atmosphere and to the Earth 

 itself, always diminishing in intensity because of the bad con- 

 ducting power of the successive denser layers of air and of the 

 crust of the Earth. That would then only be negative, as being 

 less positive than the air. The diffusion of electricity through 

 planetary space would be limited by the diffusion of matter, since 

 it cannot spread in a vacuum. 



That gaseous matter extends farther through space than the 

 distance which is generally assigned to the Earth's atmosphere 

 will be proved by the fact that Auroras, which are due to electric 

 discharges, are produced at heights of 100 and 200 kilometres, 

 where some gaseous matter must exist. 



M. de la Rive agrees with M. Becquerel as to the electrical 

 origin of the Aurora, but considers that the Earth is charged with 

 negative electricity, and is the source of the positive atmospheric 

 electricity, the atmosphere becoming charged by the aqueous 

 vapour rising in tropical seas. The action of the Sun, he con- 

 siders, is an indirect action which varies with the state of the 

 Sun's surface, as shown by the coincidence in the periods of Aurora 

 and Sun spots. 



In the accounts of travellers in Norway we often read of their 

 being enveloped in the Aurora, and perceiving a strong smell of 

 sulphur, which must be attributed to the presence of ozone. 

 M. Paul Rollier, the aeronaut, who descended on a mountain 



