There is a major "bug" with stone sense in DF2010. If you use it, when DF rechecks what you can see, it creates a lag spike. In addition and concurrent with that is that it fully reveals any underground area after a few rechecks, since DF feels that with the expanded area of vision, it should expose more. This has the interesting effect where if you have a magma pipe/underground pit/passage deeper, it can reveal every cavern and the magma sea. Once it hits the magma sea, it exposes the bottom layer of adamatine, opening up the clown car, but not completely.