“ The oldest deposits that may be included are those containing neolithic implements; deposits of historic times should also be grouped here; presumably the youngest are those to be chronicled by the last man. The Holocene formations obviously include all the varieties of deposits which are accumulating at the present day: the gravels and alluvia of rivers; boulder clays, moraines and fluvio-glacial deposits; estuarine, coastal and abyssal deposits of the seas, and their equivalents in lakes; screes, taluses, wind-borne dust and sand and desert formations; chemical deposits from saline waters ”