More Science with Peter

A Victorian dog bone.

When the polymath Peter talked us through devil's toenails and broken clay pipes a few weeks ago, it got the mind ticking over. Why is there so much pottery in our back gardens? A midden, or dump, behind a row of cottages would have been as usual as a communal water pipe or laundry. But that only accounts for a concentration of willow pattern (and fish paste bottles, and bits of bedsteads) in a small area. Most of us have broken china and bones scattered around and they're old if not ancient.

While weeding through beans in the walled garden at Marsh Hall the other day, Sharron found a femur bone, almost certainly from a dog. Peter: 'This bone is very light and porous. The holes are bigger at the ends because water has been leaching phosphates from it. It's light because it's been doing good, for the soil.'

And broken plates? 'People believed that the 'bone' in bone china would have a similar effect,' says Peter. 'But pottery has been calcified in the kiln, so it doesn't do any good at all. And it doesn't break down: it will be here for the duration, until the Second Coming.' Peter is singing with his choir in the Vatican this week – I'll see if he has any information on this when he gets back.