Scientific American Magazine

The widely acknowledged need for a separate United Nations agency-responsible for verifying and controlling disarmament agreements is intensified by the current impasse In bilateral "summit" talks

An emission nebula is a cloud of interstellar gas that shines by its own light. Each kind of ion in it has a characteristic color, and three-color photography reveals how the ions are distributed

The hairlike organelles that propel swimming cells or move liquids over fixed cells are composed of sheaves of nlicrotubules. The cilia beat when the microtubules, powered by ATP, slide past one another

Life requires nitrogen that has been "fixed" through combination with other elements. Thermodynamics imposes a constraint on all possible methods of fixation: invariably energy must be supplied

From antiquity to modern times stairways have been built by rules of thumb. A study of how people move and expend energy in going up and downstairs suggests a more rational approach to their design

Various species of birds lay their eggs In the nest of another bird, which then incubates the eggs and feeds the young. The widow birds of Africa achieve this result by some remarkable feats of mimicry

The sequence of events in the nervous system that coordinates the movements of the eyes and the head in firating a visual target has been clarified by recent experiments with monkeys

Geological changes in the level of the Mediterranean shoreline have sublnerged a number of classical sites. The investigation of one of these shallow-water ruins suggests that they would all reward study