CHAPTER II.
MR. LOWELL'S DISCOVERIES AND THEORIES, --Observatory at Flagstaff, Arizona --Illustrated book on his observations of Mars --Volume on Mars and its canals, 1906 --Non-natural features --The canals as irrigation works of an intelligent race --A challenge to the thinking world --The canals as described and mapped by Mr. Lowell --The double canals --Dimensions of the canals --They cross the supposed seas --Circular black spots termed oases --An interesting volume.