In 1929, they found a charred log near Show Low, Arizona, that connected the two patterns.
His research culminated in proving that tree ring width varies with annual rainfall.
Not only that, it varies regionally, such that all trees within a specific species and region will show the same relative growth during wet years and dry years.
Since the turn of the century, several methods to measure elapsed time have been discovered.
The first and simplest method of absolute dating is using objects with dates inscribed on them, such as coins, or objects associated with historical events or documents.
The scholar most associated with the rules of stratigraphy (or law of superposition) is probably the geologist Charles Lyell.