ABSTRACT
The practice of triangulation is usually credited to Willebord Snel van Royen, who seems to have been the first to have carried it out on a useful scale. Tycho, in Copenhagen, is known to have been familiar in turn with the writings of Gemma Frisius, and he himself carried out a triangulation project in the 1570s which in effect covered the whole of Denmark. Thomas Burnet simplified his hypothesis by claiming that the primitive Earth was practically smooth and perfectly spherical, with neither mountains nor rivers of any kind. John Keill focused on Burnet's assumption of an oviform Earth extended at the poles, and the explanation of this in terms of waters fleeing from the centrifugal force at the equator to seek a position as near the axis of rotation as possible. He also objected strongly to the idea that mountains and rivers were a mere after-effect, when to him they were so obviously created for the benefit of man.
