How did early mercury delay lines store computer data?

Early mercury delay lines stored computer data by utilizing tubes filled with mercury to hold information as ultrasonic waves.12

The mechanism functioned by placing a quartz crystal at each end of the tube. These crystals converted electrical signals into ultrasonic vibrations that traveled through the mercury, and then back into electrical signals at the opposite end. By cycling these signals between the two crystals, the system could sustain and modify the data patterns.3

This technology was a significant advancement in computer memory because it allowed for much higher storage density than earlier methods, such as using individual vacuum tubes to store each bit. However, because the data traveled as a wave through the medium, it provided only sequential access to information, meaning the computer had to wait for the required data to reach the end of the line, unlike later random-access memory (RAM) devices that allowed for direct access.314