/ 
256 JSS. Diller—Fulgurite Srom Mt. Thielson, Oregon. 
fulgurite from other natural glasses. It is doubtless due to the 
fact that the source of the heat being very limited in both time 
and space, the cooling is so sudden that there is no oppor 4 
“ate for the crystallizing forees to act before the mass is rigid, 
hat the cooling takes place very suddenly is shown by the light- 
ning tubes in loose sand where, by the electric current, the ee 
sand is thrust aside, a hole made, the sand fused, and the tube 
formed and cooled in many cases before the sand can rush to- 
ether again to fill up the hole. In some cases, however, the 
pressure of the sand is so great that the tube while soft is col- 
apsed without breaking. That the fulgurite was cooled very _ 
suddenly is shown also by the fact that when heated red hot 
for but two minutes in a Bunsen flame and then examined under 
fhe EUs tke & 
amp for nearly five hours without intermission. 
the fused mass in the lower part of the crucible was found to 
be clear and colorless, while the upper portion was tough, black e 
and basaltic in appearance. Under the microscope the dark 
colored portion was found to be crowded with distinctly striated 
feldspar microlites and a multitude of others, very minute, which 
were indeterminable, besides many minute octahedrons of mag 
netite. Between these microlites, arranged in a basaltic fashion, 
could be detected a trace of pyroxene, apparently monoclinic, 
with considerable brownish glass and dark globulitic base. 4? 
interesting feature in this section is the accumulation of the 
smallest microlites into elongated groups (fig. 2) in which all the 
individuals are parallel, as if to indicate their ultimate combit 
ation to form a single crystal. The clear and colorless porto? 
of the fused mass found upon the bottom of the crucible com” 
ST Se: 
