1832-3.] ELECTRIC PHENOMENA. 61 
dimension. They failed both with powdered felspar and quartz. 
One tube, formed with pounded glass, was very nearly an inch 
long, namely, ‘982, and had an internal diameter of -019 
ofan inch. When we hear that the strongest battery in Paris 
was used, and’ that its power on a substance of such 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 the sand in several places, has formed cylinders, in one 
instance of at least thirty feet long, and having an internal 
bore, where not compressed, of full an inch and a half; and this 
in a material so extraordinarily refractory as quartz ! 
The tubes, as I have already remarked, enter the sand nearly 
in a vertical direction. One, however, which was less regular 
than the others, 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, were 
sent off; one pointed downwards, and the other upwards. This 
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 vertical, and traced be- 
neath the 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 
twenty, situated among some high sand-hillocks, and at the dis- 
tance of about half a mile from a chain of hills four or five 
hundred feet in height. 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, isthe 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 shocks, we must believe that the 
lightning, shortly before entering the ground, divides itself into 
separate branches. 
The neighbourhood of the Rio Plata seems peculiarly subject 
to electric phenomena. In the year 1798,* one of the most 
* Azara’s Voyage, vol. i, p. 36, 
