Easton's Bible Dictionary (1897)
(Isa. 35:7), Heb. sharab, a “mirage”, a phenomenon caused by the refraction of the rays of the sun on the glowing sands of the desert, causing them suddenly to assume the appearance of a beautiful lake. It is called by the modern Arabs by the same Hebrew name serab.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
PARCH'ED GROUND. The Hebrew word thus rendered, Isa 35:7, denotes that optical delusion known by the name of "mirage," and frequently occurring in the African and Asiatic deserts. On account of the different refraction of the solar rays in the various layers of the atmosphere, the white, barren sand-waste suddenly assumes the aspect of a beautiful lake surrounded by trees and a most luxuriant vegetation.