In the 18th century, "Observations" appears in the titles of scientific works – compare Benjamin Franklin's "Experiments and Observations on Electricity" (1751) and Joseph Priestley's "Experiments and Observations of Different Kinds of Air" (1774). Priestley, Hartley's champion, would declare that Hartley's work "contains a new and most extensive "science. …" he study of it will be like entering upon a "new world. …"" The science is the science of "man", and the "new world" is the one embodied in the human "frame" itself.