A new method of operating gravity-coring tubes has been developed and tested. By means of a pilot weight and release mechanism, the coring tube with drive weight and guide vanes is released at a predetermined distance above the sea bottom and allowed to drop freely through the water. It thereby gains considerable velocity and momentum, and the energy available for forcing the tube into the sediments may be increased in this manner. This method of operation has proved to be especially valuable in coring firm sediments, in which hitherto it has been difficult to obtain a satisfactory depth of penetration with a coring tube whose downward velocity is governed by the safe speed at which a cable may be payed out. Two coring tubes of this type have been built for the Woods Hole Oceanographic Institution, and cores of bottom sediments obtained in the North Atlantic Ocean at depths up to 2250 fathoms. The general theory and details of construction and operation and some of the results obtained are described.