674 



A. A. J U LIEN 



of brownish and reddish iron-stains, and besprinkled with 

 swarms of bubbles of varying size. 



The inner surface of the lumen is for the most part smooth 

 and shining, with boundary sharply defined in cross-section 



Fig. I. — Sand-Fulgurite, Poland. X lo. Photomicrograph of cross-section. 



(Fig. i), as in other fulgurites; but, here and there, a few 

 points, pustules and needles of glass are found to project, of a 

 length up to 0.17""^. For the origin of the central lumen an 

 explanation long accepted has been that suggested by Watt for 

 the hollows in a fulgurite-mass, "the expansion of moisture 

 while the fusion existed.' In this cross-section the outline is 



"■P/iil. Trans. Roy. .Sot:. Loud., Vol. LXXX (1790), p. 302. 



