Water like a stone

I know that Christmas is now long gone but the bird bath reminded me of the carol In the Bleak Midwinter this morning . The base of the bird bath is porous and so it wasn’t really much use to the birds that frequent our garden over the summer. I put a bowl into it to hold water for the birds but this cracked and as an emergency measure I placed a flower pot saucer on it with a big stone to stop it getting blown away. I really don’t know why the second stone is there