Much of what we know about the structure of the lighthouse comes from a German scholar named Hermann Thiersch, who authored a book on the topic that remains one of the best reference works on Pharos Lighthouse to this day. There was no real lack of representations of the Lighthouse for Hermann Thiersch to use in his studies of the structure, for it was depicted on coins, mosaics and small models of it were also available. While all of these agree as to the building's basic design, none provide much detail. On the other hand, there is a surprising lack of descriptions by ancient writers and in fact most come from Arab travelers. Many of these, however, combine precise details mixed with wild fantasies. While they provide some good information on the lower levels of the tower, they provide little valuable information about the upper levels and almost nothing concerning the light source. In fact, by the medieval period the upper section had already been destroyed.
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