Abstract
Ice was grown in a cold chamber mounted on a Vickers Projection Microscope and so constructed that the temperature and humidity could be independently controlled. Observations were made (magnification 280×to 560×) of the growth of ice crystals on a freshly-cleaved mica substrate. No growth occurred until saturation with respect to water was reached; it was concluded that nucleation of ice on mica is a two-stage process above −40C. Upon subsequent regrowth of ice, certain places were observed which acted as sublimation nuclei. These results are qualitatively discussed in terms of present nucleation theory.
