44 MALDONADO. [CHAP. ra. 



glossy surface possess a metallic lustre. The thickness of the wall of 

 the tube varies from a thirtieth to a twentieth of an inch, and occasion- 

 ally even equals a tenth. On the outside the grains of sand are rounded, 

 and have a slightly glazed appearance: I could not distinguish any 

 signs of crystallization. In a similar manner to that described in the 

 Geological Transactions, the tubes are generally compressed, and have 

 deep longitudinal furrows, so as closely to resemble a shrivelled 

 vegetable stalk, or the bark of the elm or cork tree. Their circumference 

 is about two inches, but in some fragments, which are cylindrical and 

 without any furrows, it is as much as four inches. The compression 

 from the surrounding loose sand, acting while the tube was still softened 

 from the effects of the intense heat, has evidently caused the creases or 

 furrows. Judging from the uncompressed fragments, the measure or 

 bore of the lightning (if such a term may be used), must have been 

 about one inch and a quarter. At Paris, M. Hachette and M. Beudant * 

 succeeded in making tubes, in most respects similar to these fulgurites, 

 by passing very strong shocks of galvanism through finely-powdered 

 glass : when salt was added, so as to increase its fusibility, the tubes 

 were larger in every 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 of an inch. 

 When we hear that the strongest battery in Paris was used, and that its 

 power on a substance of such easy fusibility 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 1 



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 considerable 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 beneath the surface, there were several other groups of 

 fragments, 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 distance 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 

 we!! 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 

 * " Annalcs de Chimie et de Physique," torn, xxxvii., p. 319. 



