Page:Across the Zodiac (Volume 2).djvu/17

 highly organised form of vegetation than at present exists anywhere upon the surface. Intermixed with these were beds of the peculiar submarine shell-rock whose formation I have just described. Above these again come strata of diluvial gravel, and about 400 feet below the surface rocks that bore evident traces of a glacial period. As we approached the lower end of the gulf the shores sloped constantly downward, and where they were no more than 600 feet in height I was able to distinguish an upper stratum of some forty yards in depth, preserving through its whole extent traces of human life and even of civilisation. This implied, if fairly representative of the rest of the planet's crust, an existence of man upon its surface ten, twenty, or even a hundred-fold longer than he is supposed to have enjoyed upon Earth. About noon on the seventh day we entered the canal which connects this arm of the gulf with the sea of the northern temperate zone. It varies in height from 400 to 600 feet, in width from 100 to 300 yards, its channel never exceeds 20 feet in depth, Ergimo explained that the length had been thought to render a tunnel unsuitable, as the ordinary method of ventilation could hardly have been made to work, and to ventilate such a tunnel through shafts sunk to so great a depth would have been almost as costly as the method actually adopted. A much smaller breadth might have been thought to suffice, and was at first intended; but it was found that the current in a narrow channel, the outer sea being many inches higher than the water of the gulf, would have been too rapid and violent for safety. The work had occupied fifteen Martial years,