88 NOTES ON FULGURITES. 



believe to be due, as suggested bj^ Mr. Abbott, to their having been 

 formed at such a depth below the surface that the compactuess of the 

 sand i^revented their collapsing. Further examination caused me to 

 doubt this for reasons to be noted later. 



Accompanying the tubes were several small irregularly rounded 

 lumj^s of fulgurites without the tubular openings, resembling nothing 

 more than as if a ladle of the molten matter'had been poured out upon 

 the ground and " spattered," as suggested by Mr. Abbott. The largest 

 of these was some 2'=™. broad, and 5 to G""". in thickness, and weighed 

 about 2i grams. An average of four determinations on these bk'bs 

 gave a specific gravity of 2.07. 



A thin section of the largest sample showed it to be completely amor- 

 phous, with only here and thereasmall grain of sand adhering to its outer 

 surface. This glass is nearly colorless, with occasionally a brownish or 

 yellowish stain from iron oxides, and carries many bubbles. In a few 

 instances what api)ears like fluidal structure was observed, but the 

 appearance was not as if any considerable portion of the mass had 

 moved, but rather as if the sudden expansion of a steam bubble had 

 pushed the still fluid or plastic material to one side, causing a local de- 

 velopment of very limited area. The size of this mass led me to look 

 with considerable care for the presence of products of crystallization. 

 Kone such, however, were observed, either in the isolated blebs or the 

 glass of the tube walls, my own observations agreeing in this respect 

 with those of Diller, Wichmann, and others. 



The jieculiar corrugations, or wing-like projections from the sides of 

 the tubes, I cannot (in company with Wichmann) believe to be due in 

 all cases to the partial collapsing of the tube through pressure from 

 without, but rather to inequalities in the sand, together with, perhai^s, 

 unequal contraction due to rapid cooling. I cannot conceive how press- 

 ure, however applied, could give rise to such peculiar forms which have 

 an appearance, as suggested by Darwin and Fiedler, closely resembling 

 a shrunken vegetable stalk or the bark of the elm or cork tree (Figs. 1 

 and 3). The fact that these, although usually extending in a direction 

 approximately parallel to the length of the tube, start out at any point 

 in such a very irregular manner, and occasionally at very nearly right 

 angles to the length of the tube,, seems in itself a sufiScient objection to 

 this idea. Is it not more probable that they are formed by the light- 

 ning's following out the path of least resistance, causing the bore to be 

 enlarged here and contracted there in accordance with the conductibil- 

 ity of those portions through which it passed (and the amount of moist- 

 ure they contained), and that the small branches and wings, sometimes 

 mere points, are lateral off^ihoots ? The absolute contact, in some cases, 

 of the inner walls of th'e wings, togethex with the fluidal structure ex- 

 tending from within outward, as noted by Wichmann, would, it seems to 

 me, tend to prove that the.y are original structures, and in no way caused 

 by a subsequent collapsing. 1 fail, moroovei', to see that we have any 

 grounds for expecting the bore of lightning to be evenly cylindrical, 



