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We present observations of the interstellar scintillation of the 1.4-GHz emission from pulsar PSR1933+16 taken at eight epochs between January 1992, and May 1993. Accepted theory indicates that these scintillations are due to diffraction of the emission caused by free electron clouds on scales of $10^{6}$ to $10^{8}$ m, and refraction of the emission caused by free electron clouds of size $10^{10}$ to $10^{12}$ m. While diffractive effects are always visible in this pulsar's emission spectra, a single refractive event was observed in July 1992. At this epoch, the characteristic tilting by refraction of scintiles in the dynamic spectra was clearly present at the commencement of the observing session, but diminished, and ultimately disappeared, over a period of two days. Our data place strong constraints on the frequency and duration of such refractive events in this object. We calculate an average $C_{N}^{2}$ for PSR1933+16 of $10^{-2.76} m^{-20/3}$, where $C_{N}^{2}$ is the path-length-averaged strength of turbulence in the interstellar medium. In addition, the estimated average speed of the diffraction pattern transverse to the line of sight is V$_{iss}$ = 176 kms$^{-1}$. Our data on PSR1933+16 confirm the prediction from scintillation theory that the decorrelation bandwidth of the scintillations should be proportional to the square of
