THESE DAYS MAP-MAKERS are rarely the objects of vilification. That distinction tends to be reserved for other kinds of scientist, such as researchers who experiment on animals, or WMD experts. But in the sixteenth century any intellectual living in mainland Europe could find himself denounced to the Inquisition, and if his view of the world did not conform to that of the Catholic Church, he could be in mortal danger.

Gerard Mercator is not generally remembered as a religious renegade, but as the creator of the 'projection' to which he gave his name. Mercator made maps and globes of staggering beauty and accuracy (a pair of his globes can fetch $1.8 million), but it was the Mercator Projection, his method