(I) The oldest known evidence of strange flying objects is from some cave paintings that were found in Europe. (II) Before the end of the 18th century, very few Europeans had dedicated themselves to the study of flight. (Ill) One was the Italian Renaissance artist Leonardo da Vinci. (IV) He was preoccupied chiefly with bird flight and with flapping-wing machines called “ornithopters”. (V) His aeronautical work, however, remained unknown until late in the 19th century, when it could furnish little of technical value to experimenters but was a source of inspiration to aspiring European engineers.