THE RISE OF ISLAIsI 231

comes very near to the theoretical discovery of magnifying
lenses, which was made practically in Italy three centuries
later, while more than six centuries were to pass before the
law of sines was established by Snell and Descartes. Roger
Bacon < 13th century) and all medieval Western writers on
optics—notably the Pole Witelo or Vitellio base their optical
works on Alhazen's Opticae Thesaurus. His work also in-
fluenced Leonardo da Vinci and Johann Kepler.1

As often we have done in previous chapters we must reluc-
tantly bring this chapter also to a close, with a sense of in-
completeness. For a fuller survey of Muslim, particularly
Arabic, civilisation we must refer the reader to The Legacy
cj Islam (Oxford University Press). In architecture they
produced a wonder of the world like the Alhambra in
Granada. In the minor arts too they made valuable contri-
butions, too numerous to be described here. " In manufac-
tures/' one wTiter has pointed out, ik they surpassed the world
in variety and beauty of design and perfection of workman-
ship. They worked in all the metals—gold, silver, copper,
bronze, iron, and steel. They made glass and pottery of the
finest quality. They knew the secrets of dyeing. They had
many processes of dressing leather and their work was
famous throughout Europe. They made tinctures, essences,
and syrups. They made sugar from the cane and grew many
fine kinds of wine. They practised farming in a scientific
way. They had good systems of irrigation. They knew the
value of fertilizers. They fitted their crops to the quality
of the ground. They knew how to graft and were able to
produce some new varieties of fruits and flowers. They
introduced into the West many trees and plants from the
East." They also built hospitals with trained physicians and

1. Ibid., p. 334.