Reviews the Hafele-Keating experiment on relativistic changes in eastward and westward moving cesium atomic clocks. Recommends the use of the Sagnac effect to remove the east-west time asymmetry and of the general-relativistic effect to elucidate the clock-rate changes. (CC)

Describes a microbiological experiment designed to study the competition between two species of bacteria. Experimental procedures and data obtained in conducting this experiment are provided, together with a discussion of the results. (JR)

Provides description of an activity in which students synthesized sulfanilamide or sulfathiazole, II. The drug was then used as a chemotherapeutic agent. (RH)

Experiments give students a practical awareness of pollution in its different forms. (RK)

A practical magnetotropism experiment with seeds is presented. The procedures, needed controls, and observations of results are described. (DF)

The ratio of electronic charge to Boltzmann's constant can be easily determined by measuring the short-circuit collector current versus the emitter-base voltage characteristic of a silicon transistor connected in the common-base mode. (Author/DF)

Describes the theoretical principles and experimental arrangement in determining the transmission and reflection coefficients for polarizations which are parallel and perpendicular to the plane of incidence. Indicates an error of the order of five percent in the results obtained. (CC)