APPENDICES

A. METEORITES AND FULGURITES.
BY DB. L. J. SKBNOTR, F.R.S.,

Mineral Department, British Museum.

1. METEORIC mOtf AND SILICA-GLASS FEOM THE METEOBITE
CRATEES OF WABAR.

THE large piece of metal found near the craters at Wabar shows
the concave surfaces characteristic of weathered meteoric iron.
It is in part covered with rusty scale and is evidently only a
remnant of a much larger mass. As received at the British
Museum the mass weighed 25 pounds (114 kilograms). The
shape is irregular with maximum dimensions in three directions
at right angles of 10 x 6 x 5 inches. Some of the loose scale has
been cleaned off, but on one side there is a thick mass of laminated
scale with cemented sand grains. The scale is dark brown in
colour and is magnetic. After the mass was photographed
(fig. 14a) one end was sawn ofi with a hack-saw, and the two cut
surfaces were filed flat and polished. On immersing the polished
surface in a very dilute solution of nitric acid the internal crystal-
line structure of the mass was at once revealed, and the etching
was stopped after two or three minutes with the result shown in
fig. 146, The beautiful patterns shown on the etched surface
are known as Widmanstatten figures, and on this scale are to be
seen only in meteoric irons. The structure consists of alternating
bands of two alloys of iron and nickel, broader bands of kamacite
being separated by very narrow bands of bright taenite. A third
constituent occupying the angular interspaces is known as
plessite, which also consists of iron and nickel but in different
proportions. A few minute blebs of bronze-yellow troilite (iron
sulphide, EeS) are embedded in the nickel-iron. According to
their crystalline structure there are several types of meteoric
iron ; the Wabar iron is to be classed as a ' medium octahedrite/
A complex system of very fine lines (c Neumann lines ') is shown
on the bands of kamacite. These are slip bands probably pro-
duced by the shock when the meteorite struck the earth.
A detailed chemical analysis of the Wabar iron made by Mr.