" (3/10. "Geological
Transactions" volume 2 page 528. In the "Philosophical
Transactions" 1790 page 294, Dr. Priestley has described some
imperfect siliceous tubes and a melted pebble of quartz, found in
digging into the ground, under a tree, where a man had been killed
by lightning.) The sand-hillocks of Maldonado, not being protected
by vegetation, are constantly changing their position. From this
cause the tubes projected above the surface; and numerous fragments
lying near, showed that they had formerly been buried to a greater
depth. Four sets entered the sand perpendicularly: by working with
my hands I traced one of them two feet deep; and some fragments
which evidently had belonged to the same tube, when added to the
other part, measured five feet three inches. The diameter of the
whole tube was nearly equal, and therefore we must suppose that
originally it extended to a much greater depth. These dimensions
are however small, compared to those of the tubes from Drigg, one
of which was traced to a depth of not less than thirty feet.
The internal surface is completely vitrified, glossy, and smooth. A
small fragment examined under the microscope appeared, from the
number of minute entangled air or perhaps steam bubbles, like an
assay fused before the blowpipe.
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