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Show - 7 - very much less. The radiation heat transfer of 15 to 20 cal/ cm2/ day which these authors suggest seems quite out of the question. Water vapor transfer is a much more likely explanation for the amount of heat flow they observed. The variation in ^\ with different layers most probably is associated with differences in crystal structure ( Formzahl). The above analysis of internal radiation transfer receives support from the thorough treatment of the subject by Van der Held ( 10), who demonstrates that for particulate insulators in general, the radiation transfer becomes significant only at elevated temperatures ( above 100° C), and is negligible below 0° C. The mechanical and crystallographic effects of a temperature gradient in snow have also been investigated by de Quervain ( 11), This study is particularly noteworthy because it was carried out under carefully controlled laboratory conditions and because the crystallographic changes were observed in great detail by microscopic examination of snow thin sections at beginning and end of the experiment. The bulk mechanical characteristics of the snow were also quantitatively measured. Twelve different samples of homogeneous snow, prepared by sieving natural snow, were stored under various temperature and pressure environments for forty days and the changes then examined. The results of this study are summarized as follows; 1) In the absence of a temperature gradient fresh snow is transformed into a fine granular material. Hardness and strength as well as specific gravity increase considerably with a rise of temperature and load, 2) In the presence of a temperature gradient fresh snow is transformed intc a course granular material- under the conditions of the experiment mainly to depth hoar. The development of hardness and strength is checked by a temperature gradient. An increase of strength does not occur unless |