This thesis is concerned with the daily dynamics of price change and trading volume in a speculative market. The first part examines the news-driven model of Tauchen and Pitts (1983), and develops this model to the point where it is directly testable. In order to implement the test a new method for creating a price index from futures contracts is proposed. It is found that news effects can explain some but not all of the structure of the daily price/volume relationship. An alternative explanation is presented, in which the model of Tauchen and Pitts is generalized in a non-linear fashion. In the second part of the thesis, the presence of a small amount of positive autocorrelation in daily returns is exploited through the development of a timing rule. This timing rule applies to investors who are committed to a purchase but flexible about the precise timing. The computation of the timing rule is discussed in detail. In practice it is found that this timing rule is unlikely to generate sufficiently large returns to be of interest to investors in a typical stock market, supporting the hypothesis of market efficiency. However, the incorporation of extra information regarding price/volume dynamics, as suggested by the analysis of Part I, might lead to a much improved rule.