Decantation methods for separating particles extend back to ancient Greece, but no applications were made to soils or sediments until 1692. Sieves were used to separate sands in 1704. The need of understanding the composition of earths for classification was recognized in 1750. The earliest recovery of three grades by sedimentation occurred in 1784. The term "mechanical analysis" was introduced in 1800. Sieving and decantation were combined into a single technique in 1805. The first rising current elutriator was used in 1839. In 1851 Stokes' law was formulated; in 1867 it was applied to mechanical analysis. The earliest use of graphs to represent sediments was made in 1892. In the same year the centrifuge was applied to mechanical analysis. Air analyzers were introduced in 1906. In 1912 simple sedimentation cylinders reached an apex in their development. In 1915 the continuous sedimentation balance appeared, and a mathematical theory of sedimenting systems was developed. The first manometric tube was introduced in 1918. The pipette method was developed in 1922, and the hydrometer method in 1927.