Micro-oscillations in the atmosphere of the order of magnitude of minutes have been known and studied for many years. In 1936 Macelwane, and in 1939 Benioff, with their respective electromagnetic microbarographs showed that the spectrum of these micro-oscillations extends down into the order of seconds. The two different types of microbarographs respond to the same types of stimuli and low-level turbulence is an important source of the micro-oscillations. It is shown that fronts, as such, are not a source of these micro-oscillations, although micro-oscillations may accompany a front. The microbarograph has produced observational evidence supporting Haurwitz's theoretically derived conclusion that there is a similarity between internal wave patterns and convective patterns. It is shown that electromagnetic microbarographs are useful in studying cumulus activity.

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