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 formed 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 distinctly 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 portions 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 from the time of Beer and Mädler to the present day and that these stages are distinguished by the detection of essentially new and fundamental 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.
