Seventeenth-century scientists were baffled: How did the fossils of seashells find their way to the tops of mountains? Nicolaus Steno, hailed by Stephen Jay Gould as "the founder of geology," solved the puzzle, looking directly at the clues left in the layers of the Earth. Paradoxically, at the same time his ideas were undermining the Bible’s authoritative claim as to the age of the planet, Steno was entering the priesthood and rising to bishop. He would ultimately be venerated as a saint and beatified by the Catholic Church in 1988. A thrilling tale of scientific investigation and the portrait of an extraordinary genius, The Seashell on the Mountaintop is the story of how a scientist-turned-priest forever changed our understanding of the Earth and created a new field of science.