ELECTRIC RESONANCE OF MOUNTAINS. 341) 



by sparks. On the otlier hand, the plicnomenon of electricity displayed on tho 

 lakes, and on tho very dry plains of elevated plateaux, does not seem to nie of 

 the same natnre. Finally, the surprising fact of the so-called galloping elec- 

 tricity, conrsing over pi-airies, observed by M. Qni(]uerez, near Courtamon, may 

 be regarded as a variety of lightning ; a miniature lightning, resulting from 

 the fact that the electriiied cloud was grazing the earth and discliarged itself 

 over the Avhole snrface by a thousand sparks, which were seen to run along the 

 ground. It is probable that thes(> phenomena should be divided into several 

 categories, the causes of which are not identical. Some proceed from a static 

 tension, others from a series of discharges having a certain analogy to lightning. 



The phenomenon of the chani of baions or staves, in other words, the reson- 

 ance or bonrclvwuwoit of the soil, constitutes still another species. It has been 

 observed only on the summit of mountains or of culminant peaks ; never, as far 

 as I know, on plains or at the bottom of valleys. It supposes a continuous 

 dynamic action, or an efflux of the fluid towards the clouds i)y the most salient 

 terrestrial conductors, sensibly different from static tensions and abrupt discharges. 



If we collate the observations which have been above indicated, we shall dis- 

 tinguish therein several common features : 



1st. The efflux of electricity by the culminant rocks of mountains is produced 

 under a clouded sky, charged with low clouds, enveloping the summits or passing 

 at a small distance above them, but without the occurrence of electric discharges 

 above the place whence the continuous efflux is proceeding. It would seem, 

 therefore, that when this efflux takes place, it sufficiently relieves the electric 

 tension to prevent lightning from being formed. 



2d. In all the cases observed, the summit of the mountain was enveloped by a 

 shower of hail or sleet, which leads to the sui)i)osilion that the continuous efflux 

 of electricity from the ground towards the clouds is not unconnected with the 

 formation of the vapor and probubly also with that of the hail. 



At the Piz Surley and at the iS'evado de Toluca there fell a sleet or snow 

 resembling rice, and at the pass of the Jungfrau the snow fell ichistling like hail, 

 which seems to indicate that it was rather sleet which was falling than snow. 



Doubtless we should take into account the higher temperature of the valleys, 

 where the hail, proceeding to melt, turns into rain; but still we do not think that 

 in the particular cases which we have just indicated the phenomenon of rain 

 falling in the valley and that of the sleet of the isolated mountain peaks relate 

 to a condensation taking place in accordance with identical laws through tho 

 whole extent of the sky. Thus, in particular, during the observation of Juno 

 22, 1865, I saw on tiie horizon all the spires of I'ocks, although isolated and far 

 remote from one another, enveloped by a jiowdery sleet which continued for a 

 long time, while in the rest of the sky all condensation had ceased, and in the 

 vallev there fell a copious shower of rain, but of very short duration. 



Moreover, the phenomenon which passed around the summits of the rocks was 

 quite different from that which deluged the valleys. Around these lofty pyra- 

 mids there were columns of a fine sleet of great rarity ; in the valley a heavy 

 and drenching rain, such as the thin sleet of the summits would not have pro- 

 duced had it been converted into water. Around the elevated projections, 

 therefore, by which the electricity was flowing off, the condensation presented 

 the special character of being little abundant, powdery (line sleet), and more 

 persistent than in tho rest of the sky. 



The elefltric phenomenon which has been described, and which we term tho 

 electric resonance of the mountains, seems not to be rare in high regions, without, 

 however, being very fretpient. Among the guides and hunters whom I have 

 interrogated on the subject, some had never observed it; others had heard it but 

 once or twice in their lives. But it is proper to add that it is precisely on those 

 days when menacing skies repel adventurers from the highest altitudes that tho 

 phenomenon manifests itself. 



