ARE GRAPH Y. 395 



so-called canals, and rendered them unlike anything else in heaven 

 and earth. Here was a fact of the utmost significance. The curious 

 canal system was not confined to the bright regions of the planet. The 

 dark regions, too, had a canal constitution as intricate and as complete 

 as theirs and its perfect parallel. 



It is interesting to note that the dawning recognition of these 

 canals followed the same course that it had with the others. Both sets 

 were perceived as streaks and sinuousities before their strangely regular 

 character flashed upon the observer. 



As time went on it became evident that the two sets of canals form- 

 ed part of one whole. The mesh in the bright regions ended at points 

 on the so-called coast-line where the mesh in the dark regions began. 

 The system was thus knit together and made of a piece over the whole 

 surface of the planet. On the belt of narrow 'seas' lying between the 

 continent and the chain of islands to the south, it was as of a lacing 

 run through eyelets in the coast-lines giving an effect of slashed trunk- 

 hose, so singularly did the canals criss-cross them working up in a 

 zigzag progression from one end of a sea to the other. 



In 1896-7 (Map X.) the dark region canals came out still more dis- 

 tinctly and especially the oases or spots at their junctions. 



At the succeeding oppositions they continued visible and the few 

 dark areas in the northern hemisphere were found in 1899 (Map XL) 

 and still more so in 1901 (Map. XII.) to be similarly but groundwork 

 for a superposed mesh of knots and netting. No part of the somber por- 

 tions any more than of the light ones remained free of the systematic 

 triangulation. 



Furthermore each period contains within itself a progressive 

 development in particularity. Each successive opposition has made 

 the foundation it found more secure and added a superstructure 

 of its own. And what has been true of each period by itself has been 

 equally so of the three taken together. As the maps show, each has 

 been at once a review and an advance. This has been due not only to 

 increased optical facilities and improved atmospheric conditions, but 

 still more to systematic, persistent and extended work on the part of the 

 observers. 



It will thus be seen that three stages mark the advance in areography 

 fiom the time of Beer and Madler to the present day and that these 

 stages are distinguished by the detection of essentially new and funda- 

 mental phenomena : 



I. Stage of supposed continents and seas. 

 II. Stage of ' canals ' found intersecting the lands. 



III. Stage of ' canals ' found traversing the ' seas. ' 



Each of the stages is here represented by four maps, and each is an 

 advance upon its predecessor. 



