In 1836 he became attached to the Geological Survey of the State of New York .
After lengthened study he grouped the local strata ( 1842 ) into the Taconic and overlying State of New York   systems .
In 1836 he became attached to the Geological Survey of the State of New York , and after lengthened study he grouped the local strata ( 1842 ) into the Taconic and overlying New York systems .