This paper is mainly devoted to an analysis of the relationship of variati ons in mercury amounts at eight mercurometric points during the Water mercu-rometric survey performed successively in Yunnan, Beijing and Sichuan in 1986-1988 to ten earthquakes. Large quantities of data reveal the following features of mercury: the mercury amount in water suffers less interference, mercury background is stable under normal conditions, mercury is very sensi tive to a coming earthquake, its content varies remarkably, and its anomalies are recognizable. Therefore, mercurometric survey will surely become an effe ctive method for short-period earthquake prediction.. The present paper makes a description of this batch of practical data.