fectually. Just how he accomplished this
it is unsuitable to enter into here because of its extent
lest we should appear to be wandering from our main theme.

Thus, although there is a hint of mechanical complexity, there is really
no justification for such an assumption; the description might well
imply only a zodiac band on which the orbits of the planets were
painted. On the other hand it is not inconceivable that Gerbert could
have learned something of Islamic and other extra-European traditions
during his period of study with the Bishop of Barcelona--a traveling
scholarship that seems to have had many repercussions on the whole field
of European scholarship.

Once the floodgates of Arabic learning were opened, a stream of
mechanized astronomical models poured into Europe. Astrolabes and
equatoria rapidly became very popular, mainly through the reason for
which they had been first devised, the avoidance of tedious written
computation. Many medieval astrolabes have survived, and at least three
medieval equatoria are known. Chaucer is well known for his treatise on
the astrolabe; a manuscript in Cambridge, containing a companion
treatise on the equatorium, has been tentatively suggested by the
present author as also being the work of Chaucer and the only piece
written in his own hand.

The geared astrolabe of al-Biruni is another type of protoclock to have
been transmitted. A specimen in the Science Museum, London,[28] though
unfortunately now incomplete, has a very sophistocated arrangement of
gears for moving pointers to indicate the correct relative positions and
movements of the sun and moon (see figs. 17 and 18). Like the earlier
Muslim example it contains wheels with odd numbers of gear teeth (14,
27, 39); however, the teeth are no longer equilateral in shape, but
approximate a more modern slightly rounded form. This example is French
and appears to date from _ca._ 1300. Another Gothic astrolabe with a
similar gear ring on the rete, said to date from _ca._ 1400 (it could
well be much earlier) is now in the Billmeier collection (London).[29]

Turning from the mechanized astrolabe to the mechanized equatorium, we
find the work of Richard of Wallingford (1292?-1336) of the greatest
interest as providing an immediate precursor to that of de Dondi. He
was the son of an ingenious blacksmith, making his way to Merton
College, Oxford, then the most active and original school of astronomy
in Europe, and winning l