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A Chapter on Fossil Lightning
Published online by Cambridge University Press: 17 March 2016
Extract
The expression “fossil lightning” may seem somewhat paradoxical, but it is here employed in a figurative sense to designate a condition of things which we have good modern evidence to prove to have been the result of the lightning's flash, myriads of ages gone by. Of late years vitrified sand-tubes have been discovered in Cumberland, in Prussia, South America, Natal, and other places; and these have been very clearly made out as having been directly caused by lightning, and hence they have been called by mineralogists “Fulminary tubes” or Fulgurites. All these would appear, so far as we can ascertain, to have been formed at comparatively a very recent period, and hardly, therefore, deserving of the appellation of “fossil lightning.” Nevertheless, as I have come across some examples of such bodies on the surface of the flagstones which form our pavements, and of the antiquity of which there cannot be any doubt whatever, I have no hesitation in making use of the term which heads this chapter.
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References
page 196 note * Trans. Geol. Soc. vols. ii. and v.
page 196 note † The agglutinating power of the electric fluid sometimes forms a mass of 2½ inches diameter, with a tube above and below it; many such interruptions have been found in the course of a single tube, from the lightning having met with obstacles in its passage.
page 198 note * Trans. Geol. Soc. vol. ii.
page 198 note † Annales de Chim. et Phy. tom. 37.
page 199 note * Principles of Geology, 8th edition.
page 200 note * Humboldt's Cosmos, vol. i. and vol. iv.
page 201 note * Darwin's Journal, vol. iii. 1839, p. 69 Google Scholar.
page 203 note * I state this with some reservation, because I have seen a section of what looks like a lightning-tube in a sandstone door-step. It has four irregularly compressed sides, and presents very much the appearance of one of these bodies.
page 204 note * These flagstones are probably from the lower carboniferous rocks of Yorkshire; at least, nearly all London is paved with such flags.—Ed. Geol.
page 204 note † Near this spot are the remains of an old Roman encampment; and occasionally coins, with other objects of interest, are turned up.
page 204 note ∥ This instance referred to by Dr. Gibb was a case of a double or furcated perforation in a thick layer of clay covering the Castle Hill at Dover, made by a powerful stream of lightning, which, when a lad, I saw strike the ground at an elevated point. It can scarcely be called a fulgurite, as the clay was only coated on the surface with bluish-grey beads and grains, powdered, as it were, like the bloom of a peach. The perforations forked at about nine inches from the upper surface of the soil, apparently divided by one of the numerous angular fragments of flint which abound in the subsoil, and were of sufficient dimensions for me to put my arm with my walking-stick into them. The branches had divergent directions, as nearly as I can remember, of 30° or 35° on either hand from an imaginary intermediate vertical line. Their forms were irregularly angular, with ridges, as in the fulgurites, but they were of far larger diameter than any of the latter objects I have ever seen.D—S. J. M.
page 204 note § When strolling over the sand-banks of the hills at this place, when a youth, I discovered substances which I now believe were these tubes.