Earth's atmosphere, however, is not a uniform optical medium
. Variations in temperature and density create patches of air that deflect or slow the light passing through them.
They are the precursors of a new and different sensibility, and a new relationship of humanity to nature, brilliantly analyzed by Vincent Scully who argues that 'In the Italian garden, water is the awesome gift of the earth; in the French garden, water becomes primarily the optical medium
by means of which the sky is reflected'.(7) Scully describes the great canal at Versailles where 'our gaze moves rapidly down the tapis vert, but when it hits the water it literally takes off.