After the First World War interrupted oceanographic research, international scientific activities started anew in 1920. The invention of the echo sounder in 1912 reached a new significance for the international marine research. Henceforth, it was possible to measure the distance to the seabed by sending acoustic signals instead of using wires and weights. Warships used echo sounders during the First World War. In 1922, the American destroyer "Stewart" took the first echo profile over the North Atlantic and one year later, the sonic logging between San Francisco and San Diego was published. Between 1929 and 1934 the "USS Ramapo" took about thirty profiles of the northern Pacific Ocean. In 1927, the German cruiser "Emden" was able to carry out a series of soundings of the ocean trench to the east of the Philippines.