Man's physical universe



stones, preceded by four terrific explosions, occurred at Johnstown,

Colorado, on the afternoon of July 6, 1924. Many more such showers

of meteorites have been recorded.

The largest meteorite fall known in modern times fell in Central

Siberia and completely devastated an area of over 1000 square miles.

It fell on June 30, 1908, in the primeval forest of Siberia in the Province

of Yenissei. It was seen at a distance of 4000 miles. Nearly 50 miles

away people were burned by the heat. Trees over a wide area, as well

as a herd of 1500 domesticated reindeer, were destroyed. The shock

Fig. 32. Meteor crater from the air near Winslow, Arizona. (From the Yerkes

Observatory', reprinted by permission of the Chicago University Press.)

produced by the meteorite was registered by a seismograph at Irkutsk,

600 miles distant, while the air-compression wave was registered by a

barograph in the same city.

did not fall in a densely populated area.

It is fortunate, indeed, that this meteorite

The Origin of Tektites Is Still a Mystery.

Many years ago the peasants of Bohemia occasionally plowed up

curious pieces of rough green glass in deposits which were laid down

before man learned how to make glass. More recently thousands

of similar small glassy objects called "tektites" were discovered in

Australia, Tasmania, British Borneo, China, Texas, Sweden, and other

parts of the world.

At one time these tektites were thought to be of volcanic origin, but

most of the tektite areas are free of volcanic activities. Another theory

is that these glassy objects are meteorites that melted when they

reached the earth's atmosphere.

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