29 
gtetronomp 
Four lectures were delivered during the session. Our thanks are again due 
to Mr. W. H. Day, f.r.a.s., whose subject was '"Spiral Nebulae to External 
Galaxies". The other three lectures were given by the Chairman. It may be of 
interest to members to know that he has now built a new 12-inch telescope in his 
observatory at Christchurch. He hopes that the weather will be kinder than it has 
been, for occluded skies have prevented the section meetings which had been 
arranged at his observatory. 
C. M. Pither 
THE MYSTERIOUS TEKTITES 
Abstract of a lecture given by the Chairman on October 7th 
Tektites are small glassy objects which are found in various parts of the globe, 
and are all, except for the Moldavites which are a beautiful transparent green, 
blackish opaque in colour. The name tektite, which was coined in 1900 by 
F. E. Suess from a Greek word meaning 'melted', indicates that their appearance 
is that of once melted glass; the composition is actually in the region of 70% 
to 97% silica. The shapes of tektites vary considerably, being spherical, tear-drop, 
or dumb-bell; others are sometimes button-shaped or cylindrical. 
Tektites are found only in certain parts of the world which are within a band 
of 45° either side of the Earth's equator and are normally found within deposits 
of sand or gravel. The name is used to describe any such objects no matter where 
they are found, with additional group names to indicate their location. Below will 
be found the eight known tektite fields, together with their group names and in 
some cases their sub-group names : 
Main Location Group Sub-group Location Sub-group 
Czechoslovakia Moldavites 
Indochina Indochinites Philippines Phiiippinites 
Indochina Indochinites 
Isle of Biiliton Billitonites 
Java Javarites 
Texas Bidiasites 
Australia Australites 
West Africa Ivory Coast Tektites 
It is widely thought that tektites fell to Earth from space, perhaps in a 
similar way to meteors, but they differ greatly from meteors. They rarely exceed 
2 to 2\ inches in diameter and normally weigh from 1 to 100 grams, whilst meteors 
can range from grains of sand to objects weighing several tons; another difference 
is that the tektites have non-random distribution, whereas meteors can fall, and 
do, on any part of the Earth's surface. Laboratory tests indicated another differ- 
ence, which relates to the speeds of the particles as they pass through our 
atmosphere, for it was shown that the velocity of a tektite would have been 
4| to 61 miles per second, whereas the known velocities for meteors are from 
1\ to 43| miles per second. 
We have all witnessed the arrival of a meteor into the Earth's atmosphere. 
Such a "shooting star" appears as a very short-lived burst of light streaking across 
the sky. Unfortunately no tektite has ever been seen to arrive on Earth; in fact 
all the tektites which are found today are of very great age. The laboratory test 
used to give some determination of the age of tektites is the measurement of the 
build-up of argon —40 from the decaying radioactive nuclide potassium —40. 
From this the following broad picture has been found : Australites— 600,000 years, 
Indochinitesf— 600,000 years, Ivory Coast Tektites — 1,300,000 years, Moldavites 
—15,000,000 years, Bediasites— 34,000,000 years. 
The origin of tektites is still much of a mystery, but laboratory tests have 
shown that they do not contain the radioactive nuclide aluminium —26, which 
occurs as a result of very long bombardment in space by cosmic rays. Thus it 
has been estimated that the tektites could not have been in space for more than 
10,000 years. In astronomical terms 10,000 years is but a passing moment and it 
has been worked out that such a period of time as this would mean that the 
tektites could not have travelled much farther than our own Moon. 
