GIBB — A CHAPTER ON FOSSIL LIGHTNING. tiOS 



several distinct currents, which would enter the surface at the 

 distance of many yards from each other. 



The greatest depth to which the electric fluid has penetrated verti- 

 cally, as demonstrated at Drigg, is forty feet ; but I should be 

 disposed to estimate the length of horizontal fusion at a much greater 

 amount. 



The majority of the fulgurites which I have had the opportunity of 

 examining, have entered the sand vertically ; but some, again, ran 

 along the surface of the sand in a horizontal direction. And it is 

 this latter form only that we can expect to meet with in a fossil state. 

 As examples of horizontal recent tubes, I may refer to specimens from 

 Dresden, in the British Museum and in the Museum of the Geological 

 Society. In the former collection the tube is very small, and runs in 

 a somewhat tortuous manner, giving off a small branch five inches 

 long, the entire length being sixteen feet and two-thirds ; but the 

 original must have been very much longer, as this is but a portion of 

 it. This example was presented by Dr. Fiedler, who has published 

 a work on fulgurites in German, to which I have not had access ; 

 but was obtained " on the confines of Holland, in a sandy country ; a 

 shepherd, after having seen the lightning strike a hillock of sand, 

 found, in the very point where it struck, a fulgurite." The Geological 

 Society's specimen is eighteen inches long, and as large as a lead- 

 pencil. Both of these examples are solid, without any internal cavity, 

 and it seems a question in my mind whether actual tubes are ever 

 found in any other than a vertical position. The examples in a fossil 

 state which have come across my notice, and which first drew my 

 attention to the subject, appear to have been found only in the solid 

 form,* and partaking of the horizontal position. There are three 

 flagstones on the eastern side of Tottenham Court Road which con- 

 tain fulgurites of a lightish colour, running in forked directions. 

 There is one on the eastern side of Russell Square, close to Guildford 

 Street, on the surface of which a dark ferruginous tube of " fossil 

 lightning " runs diagonally across the stone, its diameter being about 

 two lines. I have noticed them in three or four other places in the 



* 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 inegularly compressed 

 sides, and presents very much the appearance of one of these bodies. 



