Since its discovery in 1946 over 400 papers have been published on nuclear magnetic resonance of which more than 50% are related to problems in the structure of matter. This fact illustrates the scope of this comparatively new technique in the field of structural investigations. In addition nuclear magnetic resonance can give information concerning molecular motion in the solid state. The work reported in this thesis is concerned with this field of research. An account is given of the application of nuclear magnetic resonance to the study of single crystals of Urea and Rochelle Salt.