86 



NOTES ON FULGURITES. 



ments. The tube was about three-eigbtbs of an incb in diameter and 

 the enbirgements about three-fourths of an inch in diameter (see Fig. — ), 

 and their distance apart about 4 inches. They corresponded to the strati- 

 fication of the sand, and were without doubt caused by it." (See Fig. 

 2 of plate.) 



To ascertain the comparative composition of the gbiss and sand a 

 quantity of fragments were taken, and after pulverization and separa- 

 tion in the usual manner by the double iodide of mercury and potas- 

 sium solution, the glass, together with a portion of the sand in which 

 they were formed, was submitted to Professor Clarke, of the Geological 

 Survey, for examination, with the results given below : 



Ignition . . . . 



SiOs 



reii03*Al203 



CaO 



MgO 



K2O 



NajO 



* Wichmann found the silica percentage of fulgurite glass from Senner Heiile to be 96.44; from El- 

 Bpect, 94.26; from Starczynon, 91.23. He does not give the composition of the sand in which they 

 formed {op. cit., ]> 854). 



Harting gives the composition of the Elspect fulgurites (presumably both fn.sed and unfused por- 

 tions) as follows: Si02, 90.2 per cent. ; Al^Uj, 0.9 per cent. ; FeMj. 0.7 per cent. ; CaO, 0.1 per cent. ; 

 MgO, 5 per cent.; KO, 0.5 percent.; NaO, 0.6 percent ; Insol.— HCl, 0.9 percent.; carbonaceous 

 matter, 5.6 per cent. In the Annual Eecoid of Science and Industiy for 1874, p. 228, it is slated 

 that an:tlysis of fulgurites made by Scholz showed them to consist essentially of "carbonates of the 

 alkaline earths, about 85 per cent, being caibonate of lime and 11 per cent, carbonate of strontia." (?) 



The results being somewhat diiierent from what was anticipated, and 

 fearing there had been some mistake, and that the sand was not the 

 same as that in which the fulgurite formed, I wrote again to the Messrs. 

 Abbott, one of whom kindly visited the locality a second time and ob- 

 tained a further supply of material. He also visited another sand bank 

 about 1 mile distant, and obtained there also samples of both sand and 

 fulgurite. These last were very frail, about P'" in diameter, quite 

 cylindrical, and free from corrugations. Mv. Abbott states he does 

 not consider them "main tubes," but as branches; moreover, they did 

 not pass perpendicularly into the sand, nor was their angle of dip con- 

 stant, but varied from a few degrees from the perpendicular at the sur- 

 face to within 10 or 15 degrees of the horizontal. The two branches 

 were about 2 rods apart, one dipping to the southwest and the other 

 almost to the east. 



These branches were followed down to distances Of 3 or 4 feet below 

 the surface, and samples of both fulgurite and the inclosing sand for- 

 warded to the Museum. Portions of these were pulverized as before 

 and separations made. Some difficulty was experienced in getting a 

 sufficient quantity of material for analysis, since, owing to the varying 

 specific gravity of different portions of the glas^ caused by the included 

 cavities, portions came down with the still unfused quartz kernels, while 

 others floated to the very last. Two precipitations were made and laid 



