These green spots in the great deserts are the counterparts of Islands in the oceans.  
If not thrown up and fed by water upheaval¹, how are they produced? Are they volcanic²? The Oasis³ of Ammonium, or Siwah, six miles long and eight wide, contains the ruins of the famous temple and oracle⁴ of Ammon, visited by Alexander the Great, and celebrated⁵ for the fountain of the Sun, whose w............