While walking towards a small lake in a meadow I could hear popping and crackling in the bog as if water were boiling, though in many places there was only sludge as the water had dried up. When I looked I saw that the whole ground was almost covered with snails and it was them that were making such a noise. I noticed the same thing in other similar places and, in places where nothing showed, if I dug down into the sludge I could see that it was full of them. They dig themselves down deeper as the water dries up and this is why they are to be found in their thousands in previously dry places as soon as water comes – a claim that I had often had my doubts about in the past.