Marine creatures often make their shells or skeletons from calcium carbonate, yet the sea floor under deep water sees very little of it. In their long fall from the surface, the shells of these creatures lose carbonate to deep, high-pressure water, which dissolves much more carbon dioxide than surface water. This gives soluble calcium bicarbonate. Similarly, deep sea water dissolves much more oxygen than surface water, and high-pressure oxygen solution dissolves organic matter very efficiently.

All this implies that deep seawater is actually quite a corrosive medium, although rather slow in its action. This might explain the delayed failure of deep-sea cables, and the lack of organic detritus on the ocean floor as a whole. Over the aeons it has simply been dissolved in the water. The hydrogen sulphide of 'black smoker' springs must also have played its part.

It struck Daedalus that the mass of human rubbish now piled into landfills or inefficiently burnt could instead be dumped at sea. Even modern mariners have learnt that “over the side is over”, so new ships strive to be self-contained. The rumour that the path of the great liners from Sydney to Tilbury could be traced by the crockery and cutlery they left on the ocean floor, to avoid washing it up, will never now be verified.

So DREADCO oceanographers are lowering assorted human rubbish in stout wire baskets to the ocean floor, to judge the rate of its decomposition. With luck, many food residues and organic nasties will be swiftly dissolved. So will some ceramics and plastics. The workers will closely study the way water penetrates into each object. The crucial components may be the metals themselves — do they dissolve or stay coherent? Many of the wooden ships sunk in numerous wars seem not to have left much metal behind them; cannon extracted from centuries-old sunken frigates are claimed to ignite when exposed at last to air. This suggests that metals undergo remarkable chemical changes when kept for centuries under water.

The DREADCO researchers hope to show that much of the world's rubbish — food, cans, bottles, paper and plastics — can be safely disposed of on the deep ocean floor. It would also be fitting that Greenpeace, which forced Shell to beach an outmoded oil platform instead of dumping it on the ocean floor, should be shown to be precisely wrong.