[MOST living things exist within a fairly narrow…]

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MOST living things exist within a fairly narrow range of conditions - usually about 10 degrees Centigrade to 40 C, though warmblooded animals can survive lower temperatures and some others can survive freezing by developing their own 'anti-freeze' But the weirdest creatures I had heard about were those single celled algae and bacteria found growing happily in volcanic hot springs at temperatures of up to 100 C.

Now, ordinarily, the constituents of cells could not cope with such temperatures - the fats would melt, the proteins would unravel and coagulate like boiled egg white. So these thermophilic (heat-loving) life forms have developed fats with higher melting points and proteins that are more stable.

For a long time, it seemed that 100 C (the boiling point of water) was the upper boundary to life, ship. but recently new forms of life have been found growing around cracks in the earth's crust on the ocean floor, where the sea-water is heated to great temperatures as it cools the molten rock.

Many new and bizarre species have been found living round these gushes, all depending on the energy from the inside of the earth (just as we depend on the sun's energy). But most bizarre are the bacteria found actually living in the hot water at 250C!

This is 480 degrees Fahrenheit (Gas Mark 9), 150 C above the normal boiling point of water, and above the temperature at which paper catches fire in air (according to Ray Bradbury in Fahrenheit 451').

So how do these bacteria survive at temperatures where not only do fats melt and proteins cook, but DNA falls apart? Part of the answer must be the enormous pressures at which they live. Inese pressures prevent the superheated water from turning into steam and may help to prevent these destructive changes.

But undoubtedly these bacteria have also developed unique constituents to build their proteins etc. together more strongly.

This discovery of a hitherto unsuspected life form suggests that life may have actually been able to develop when the earth was considerably hotter than it is today.

WHETHER safe nuclear power is possible is one question, but I feel it is true to say that the Pressurised Water Reactor is more dangerous than the Advanced Gas-Cooled Reactor (Magnox), the first generation of British nuclear reactors.

So it is interesting that while the CEGB is busy buying a PWR from the Us, the National Nuclear Corporation is selling a Magnox reactor to the Turkish generals. Magnox reactors are very good at producing weapons-grade plutonium, worrying given the nature of the Turkish junta. ing.

In South Africe