One of the most exciting discoveries in marine geology in the last decade is the active hydrothermal systems at mid-ocean ridges where massive thermal springs are flowing out of the ocean floor. Scientists are now attempting to learn more about the details of these systems - what chemical reactions occur within these systems and what volumes of water are involved and for what duration. To learn the answers to these questions, the Ocean Drilling Program has set a high priority on drilling these systems. Von Herzen and Cann will design equipment to measure physical parameters (temperature, pressure, flow velocity, electrical conductivity) and obtain fluid samples in holes drilled in hydrothermal upflow zones of the sea floor.