Appendix Two to Darwin’s The Voyage of the Beagle

H.M.S. Beagle

A was listening to Charles Darwin’s The Voyage of the Beagle, an incredible story of a round the world voyage of exploration that began in 1831 and continued for five years.

The end of the edition I was listening to had two appendices, the first being nautical stuff about the trip and the second being a reprint of the ship captain Robert Fitz Roy’s “Remarks with reference to the Deluge”. It’s basically a argument for literal biblical creationism by Fitz Roy, and it was pretty ironic to find it tacked on to the Voyage. I don’t know the which editions carried it, apparently the Voyage was published in several editions (wikipedia).

The strangest part of Fitz Roy’s argument was his attempt to describe a plausible way that the biblical Deluge, the business with the Ark and world covered by water, could have deposited the many layers of rock and sediment that compose the geological record and which he observed at locations around the globe. In his argument he mentions that the Library of Useful Knowledge, 1829 describes an experiment by Perkins that showed that at a depth of 3000 feet, water is compressed to 1/27 of its volume at the surface. Fitz Roy relates this to a sailor’s experience that in determining depth with a weight and a line, larger weights are required for deeper depths.

Fitz Roy then argues that sea water is very dense in the ocean depths, and that all sorts of objects immersed during the Deluge would sink to a depth where the water was dense enough to make then buoyant, different objects finding a different natural depth, and that these layers would be preserved as the Deluge ebbed.

This is quite remarkable. Water is known now to be nearly incompressible, around 2% at the bottom of the ocean, with the slight changes in ocean water density caused more by temperature and salinity than pressure. This means that Fitz Roy’s argument falls apart. More remarkable is that such a basic fact about water and the oceans was unknown in the 1830’s. Fitz Roy really believed there was a depth in the ocean where cannon balls float, accumulated from the world’s shipwrecks and banging around together in a layer where iron floats in the deep ocean.

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