Stukeley was adamant that Stonehenge was pre-Roman (a view held by some at the time). He believed that it was constructed about 460 B.C. (currently it is believed that it dates back as far as 3000 B.C.) He arrived at this date by assuming that the builders had a knowledge of the compass, and by extrapolating variations in magnetic north, which he incorrectly assumed occillated in a regular pattern (today we know that the magnetic North pole moves somewhat at random). However, this was one of the first attempts to associate the alignment of the monument with some natural phenomena, and to use it to date the structure. (Excerpt from Book)