128 On the Humming produced on Mountains by Electricity . 



We will not here speak of the storm during which Colonel 

 Buchwalder and his aide were struck dead on the Sentis, be- 

 cause then a phenomenon was involved belonging rather to the 

 nature of a discharge of lightning. But the lighting up of 

 the rocks by night is probably due to a flow off of electricity 

 from the highest points. M. Fournet cites on this point 

 the beautiful illumination of the rocks of the Grands Mulets 

 (Mont Blanc) observed by Mr. Blackwall on the night of the 

 11th of August, 1854, and which was accompanied by sparks. 

 And, besides, the phenomenon of electricity seen on the lakes and 

 very dry plains of elevated plateaus appears to us of the same 

 nature. Finally, the curious fact of moving electricity coursing 

 over the prairies observed by M. Quiquerez near Courtamon may 

 be likened to a kind of lightning, a discharge in miniature, re- 

 sulting from the electrified cloud brushing over the earth and 

 discharging itself over its whole surface by a thousand sparks 

 which were seen to course over the meadows. It is possible 

 that these phenomena ought to be divided into several catego- 

 ries of which the causes are not the same. Some arise from 

 statical tension, others from a series of discharges which have 

 some analogy with lightning. 



The phenomenon of the singing of the staves, or of the hum- 

 ming of the soil, constitutes yet another kind. It has been ob- 

 served only on the summit or culminating ridges of hills ; never, 

 to my knowledge, in the plains or at tie bottom of a valley. It 

 supposes a continuous dynamical action, like a now of electricity 

 towards the clouds through the most salient terrestrial conductors, 

 and is different from static tension or discharge by a spark. 



Comparing the observations we have related, we remark several 

 points they have in common. 



1. The flow-off of electricity from the highest rocks on moun- 

 tains takes place under an overcast sky with low clouds enve- 

 loping the summits or passing a little above them, but without 

 electrical discharges taking place above the point where the 

 continuous electrical flow occurs. It seems, then, that when 

 this flow is able to occur, it lowers the electrical tension suffici- 

 ently to prevent the disruptive discharge occurring. 



2. In every case observed the top of the mountain was enve- 

 loped in a shower of frozen sleet, which might make one suppose 

 that the continuous flow of electricity from the ground to the 

 clouds was not unconnected with its formation, and most likely 

 also with the formation of hail. 



" Sur les phenomenes electriques qui accompagnent les orages a de grandes 

 altitudes," where these observations are collected and brought together. 

 Geneva, 1865. 



