The observed length of
their courses in the atmosphere varies from fifty to five hundred
miles. If they continued a long time in flight after entering the air,
even the largest of them would probably be consumed to the last scrap,
but their fiery career is so short on account of their great speed
that the heat does not have time to penetrate very deeply, and some
that have been picked up immediately after their fall have been found
cold as ice within. Their size after reaching the ground is variable
within wide limits; some are known which weigh several tons, but the
great majority weigh only a few pounds and many only a few ounces.
Meteorites are of two kinds: stony meteorites and iron meteorites. The
former outnumber the latter twenty to one; but many stone meteorites
contain grains of iron. Nickel is commonly found in iron meteorites,
so that it might be said that that redoubtable alloy nickel-steel is
of cosmical invention. Some twenty-five chemical elements have been
found in meteorites, including carbon and the ``sun-metal,'' helium.
The presence of the latter is certainly highly suggestive in
connection with the question of the origin of meteorites. The iron
meteorites, besides metallic iron and nickel, of which they are almost
entirely composed, contain hydrogen, helium, and carbonic oxide, and
about the only imaginable way in which these gases could have become
absorbed in the iron would be through the immersion of the latter
while in a molten or vaporized state in a hot and dense atmosphere
composed of them, a condition which we know to exist only in the
envelopes of the sun and the stars.
Pages:
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180