Green Lake is the deepest lake in Wisconsin. Its waters are "hard" and large quantities of calcium carbonate are precipitated. Deposits of this sediment are either in the form of shells of gastropods and pelecypods or small crystalline particles which have no known connection with the shells. Deposition of calcium carbonate extends from the shore to the greatest depth in the take--237 feet--with the most extensive distribution between depths of 12 and 30 feet. Sands deposited in the lake are not well sorted. Most characters of the sands were produced in other environments. Only the poor sorting and the stratification are due to lacustrine conditions.