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 those microscopic workers. These walls were exclusively the work of madrepores known as “millepores,” “porites,” “astrea,” and “meandrines.” These polypes are chiefly developed at the moving and higher beds of the ocean, and consequently it is their upper parts which commence these works, and which are buried by degrees with the débris of the secretions which support them. This, at least, is the theory of Mr. Darwin, who thus explains the theory of “atolls.” A better theory, as I think, is that the madrepores have as a basis the summits of mountains or volcanoes upon which to work, and which are at some distance below the surface.

I was enabled to observe these curious walls very closely, for in perpendicular depth the soundings gave more than 300 yards, and our electric light made these brilliant calcareous masses gleam again.

Replying to a question of Conseil’s, respecting the time these barriers had taken to construct, I astonished him somewhat by telling him that savants estimated the progress at the eighth of an inch in a hundred years.

“Then to build up these walls,’ he said, “it must have taken”

“One hundred and ninety-two thousand years, my brave friend, which lengthens the Biblical days. Moreover, the formation of the pit-coal—that is to say, the mineralisation of the forests buried by the deluge—has required a much longer time. But I may add that the Biblical days are not the epochs, and not the interval of time between sunrise and sunrise; for, according to the Bible itself, the sun was not made upon the first day of the creation.

While the Nautilus remained at the surface of the