 which drove us back to our starting point. Yet that was our good fortune. For we found close at hand the road taken 300 years before by Arne Sacknessen, the road to the centre of the earth. To our dismay, the way ahead was blocked by a huge mass of granite. There was no way round it or under it or above it. Nor was there any hope of moving it with pickaxes. I said to the professor...