Stratigraphy
The earth's crust reveals its secrets to miners, picking at layers of coal. Industrial expansion in the 1700s led to increased geological work for practical reasons, including mining and the cutting of canals. Geologists described and mapped the strata, discovered many fossils, and categorized the types of rock. They began to include ideas about the origins of types (sedimentary, volcanic) in their classifications. This is the beginning of an historical vision of the earth. The data necessary to see deep time are the analyses of strata as layers laid down by dynamic causes. It was the 17th-century naturalist Steno who articulated the principles of stratigraphy:
The Principle of Superposition
"...at the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being formed, none of the upper strata existed."
Principle of Initial Horizonatality
"Strata either perpendicular to the horizon or inclined to the horizon were at one time parallel to the horizon."
Principle of Strata Continuity
"Material forming any stratum were continuous over the surface of the Earth unless some other solid bodies stood in the way."
Principle of Cross-Cutting Relationships
"If a body or discontinuity cuts across a stratum, it must have formed after that stratum."
Mapping strata became the key to articulating this knowledge, and providing comparative data. Natural philosophers such as John Strachey in England drew on miners' practical knowledge, and their names for coal seams and other layers encountered in their mines. An early example of local stratigraphy is Strachey's publication in 1719 in the Philosophical Transactions of the Royal Society. Note the recognition of consistent layers in a locality, despite surface disruptions and alterations (as suggested by Steno).
Continued gathering of stratigraphic data in mines allowed finer and finer mapping across landscapes, leading to the possibility of comparing different regions. Recognizing the continuity of formations and sequences of layers, John Whitehurst in his Inquiry into the Original State and Formation of the Earth; Deduced from Facts and the Laws of Nature(1778) was able to predict the existence of a coal seam in a new site, based on the knowledge of a sequence above a particular known stratum of limestone. Geologists used physical, mineralogical, and chemical properties to identify these layers, and worked to produce a coherent classification scheme for naming them. Another example of a local stratigraphic map applied to coal mining is from Barthélemy Faujas de Saint Fond's A Journey through England and Scotland to the Hebrides (1799):
This map is of the Paris region, first published by Cuvier and Brongniart in 1808.