19/21 As they first appeared, so they lie. Crystallizing as they cooled, they have stereotyped in imperishable characters the aspect formerly presented by the whole Moon's surface under the influences of recent plutonic upheaval. The distance separating them from the peaks of _Tycho's_ concentric terraces was not so considerable as to conceal the principal details from a very satisfactory view. They could easily distinguish the annular ramparts of the external circumvallation, the mountains buttressing the gigantic walls internally as well as externally, the vast esplanades descending irregularly and abruptly to the sunken plains all around. They could even detect a difference of a few hundred feet in altitude in favor of the western or right hand side over the eastern. |