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POPULAR SCIENCE MONTHLY. 



In 1894 (Map IX.) Douglass at Flagstaff discovered a fact which 

 did for the dark regions what Schiaparellrs canals had done for the 

 light ones. He found on scrutinizing the southern dark areas that 

 Pickering's river-systems, which he too had seen in 1892, came out 



Map 11. Lowell, 1899. 



again and proved to be but part and parcel of a systematic set of lines 

 networking those areas. He noted that these lines were not only simple 

 streaks, but that they had nothing irregular about them, and could not 

 possibly, therefore, be the river-systems supposed by Pickering. The 

 lines were straight, equable in width and connected with one another at 



Map 12. Lowell, 1901. 



certain determinate points. They followed apparently arcs of great 

 circles and covered all the dark regions which could be well seen with a 

 singularly symmetric mesh. In other words, they presented all those 

 strange, peculiar and enigmatic characteristics which distinguished the 



