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Published online by Cambridge University Press: 19 March 2018
The term ≪ astronomical turbulence ≫ may be interpreted in a variety of ways. For the purposes of this paper, it is assumed that this expression is equivalent to the term ≪ velocity fields ≫. Thus this paper will summarize our knowledge of (i) the magnitudes of the velocities occurring in the atmospheres of reasonably stable stars, (ii) the time-dependence, and (iii) the directional characteristics of the velocity fields that exist. Neither motions in the atmospheres of explosive variables, nor motions in the atmospheres of strictly periodic variables, nor solar phenomena will be discussed. This summary is restricted to spectrographic observations of stars that have not changed their character radically since they were first observed some fifty or sixty years ago. The stars which are studied can hardly all be classified as stable stars, for changes do occur in their light and spectrum, but in no case are the changes catastrophic.