Complex sentence: In 1740 the site was surveyed and mapped by John Wood, the Elder, who noted the different stones used and suggesting the layout was based on the Pythagorean planetary system, and thought it was used as the Druid's "University".
Split into simpler sentences: In 1740 the site was surveyed and mapped by John Wood, the Elder, who noted the different stones used. He suggested the layout was based on the Pythagorean planetary system, and thought it was used as the Druid's "University".