Small as they appear to us, a little calculation must convince you that they are in some places hundreds of miles in length, a mile in width and probably in many points several miles in depth.

Their width and depth, however, vary, though their sides, so far as observed, are always rigorously parallel.

Let us take a good look at them." Putting the glass to his eye, Barbican examined the clefts for some time with close attention.

He saw that their banks were sharp edged and extremely steep.

In many places they were of such geometrical regularity that he readily excused Gruithuysen's idea of deeming them to be gigantic earthworks thrown up by the Selenite engineers.