 Picking up the Observations, such a reader would see that the book presented itself as Newtonian science—through the use of “Observations” in the title (compare two groundbreaking scientific texts, Franklin’s Experiments and Observations on Electricity, 1751, and Priestley’s Experiments and Observations of Different Kinds of Air, 1774), and through the geometrical format of propositions and corollaries that structure the text. Were he to page through the opening sections, he would see that the Hartley wrote for a reader already familiar with technical concepts in, for example, anatomy and physiology, and in the speculative physics in Newton’s Opticks.