1832-3.] ELECTPxIC PHENOMENA. 61 



dimension. Tliey failed botii with powdered felspar and quartz. 

 One tube, formetl with pounded glass, was very nearly an incli 

 ]owr. nanielv, -982, and had an internal diameter of -019 

 of an incii. Wiien we hear that the strongest battery in Paris 

 was used, and that its power on a subslance of sueli easy fusi- 

 bility as glass was to form tubes so diminutive, we must feel 

 greatly astonished at the force of a shock of lightning, which, 

 striking tlie sand in several places, has formed cylinders, in one 

 instance of at least thirty feet long, and having an internal 

 bore, wliere not compressed, of full an inch and a lialf; and this 

 in a material so extraordinarily refractory as quartz ! 



The tubes, as 1 have already remaiked, enter the sand nearly 

 in a vertical direction. One, however, which was less regular 

 than the otiiers, deviated from a right line, at the most con- 

 siderable bend, to the amount of thirty-three degrees. From 

 this same tube, two small branches, about a foot apart, wx^re 

 sent off; one pointed downwards, and the other upwards. Thi:» 

 latter case is remarkable, as the electric fluid must have turned 

 back at the acute angle of 26^ to the line of its main course. 

 besides the four tubes which I found verUcal, and traced be- 

 neath tlie surface, there were several other groups of frag- 

 ments, the original sites of which without doubt were near. 

 All occurred in a level area of shifting sand, sixty yards by 

 twentv, situated among: some hi"h sand-hillocks, and at the dis- 

 tance of about half a raile from a chain of hills four or five 

 hundred feet in heifjht. The most remarkable circumstance, as 

 it appears to me, in this case as well as in that of Drigg, and in 

 one described by M. Ribbentrop in Germany, is the number of 

 tubes found within such limited spaces. At Drigg, within an 

 area of fifteen yards, three were observed, and the same number 

 occurred in Germany. In the case which I have described, 

 certainly more than four existed within the space of the sixty by 

 twenty yards. As it does not appear probable that the tubes are 

 produced by successive distinct shoctcs, we m.ust believe th.at the 

 lightning, shortly before entering the ground, divides itself into 

 separate branches. 



The neighbourhood of the Rio Plata seems peculiarly subject 

 to electric phenomena. \\\ the year 1793,* one of the most 



* Azara's Voyage, vol. i. p. 36. 



