Hydrological soundings. This artwork is from the 1689 second edition of Telluris Theoria Sacra (The Sacred Theory of the Earth) by the English theologian Thomas Burnet (c.1635-1715). This work, first published in 1681, was one of the most popular works on geology in the 17th century. Burnet claimed that the deluge (Noah's Flood) was caused by waters rising from within the Earth. The book also contained descriptions of scientific methods, such as the one shown here. The artwork at bottom shows water depth measurements using sounding lines, and the one at top shows land elevation as well as water depths.