Reasons for color in sedimentary rocks are explored. Graphs relating the color of rock and corresponding organic content and oxidation state of iron, and of the temporal evolution of a rock sample, are presented. The development of these graphs is discussed. (CW)

In a previous article in this journal (Vol. 17, p358, 1979), a wet-bulb depression table was recommended for two simple experiments to determine relative humidity. However, the use of a graph is suggested because it gives the relative humidity directly from the wet and dry bulb readings. (JN)

Presented is an activity in which a mystery setting is used to motivate students to construct their own decay curves of melting ice used as an analogy to radioactive decay. Procedures, materials, apparatus, discussion topics, presentation, and thermodynamics are discussed. (CW)

This document contains 36 programs and/or material listings that were nominated by at least three persons and for which there was evidence of the quality of the program or materials. Reviewers looked for positive evaluation data on the impact of the materials on students, or other information that assessed the quality of the program or materials,…