Advantages of representing ternary and quaternary composition diagrams by means of rectangular coordinates were pointed out in a previous paper (EJ 288 693). A further advantage of that approach is that analytic geometry, based on rectangular coordinates, is directly applicable as demonstrated by the examples presented. (JN)

Considers the electrostatic problem of a point charge in a domain bounded by conducting planes. Lists all such domains for which a solution by images exists, describes the image charge arrays in familiar crystallographic terms, and gives an illustrative example. (Author/GS)

Presented is an activity in which students make models of viruses, which allows them to visualize the shape of these microorganisms. Included are some background on viruses, the biology and geometry of viruses, directions for building viruses, a comparison of cells and viruses, and questions for students. (KR)

Instructions are given for constructing two models, one to illustrate the general principles of symmetry in T=1, T=3, and T=4 viruses, and the other to illustrate the disposition of protein subunits in the T=3 plant viruses and the picornaviruses. (Author/CW)