Polycrystalline blocks of ice have been tested under compressive stresses in the range from 1 to 10 bars at temperatures from —13°C to the melting-point. Under these conditions ice creeps in a manner similar to that shown by metals at high temperatures; there is a transient creep component and also a continuing or quasi-viscous component. The relation between the minimum observed flow rate έ, the applied stress σ and the absolute temperature T is έ = B exp ( - Q / RT ) σ n , where R is the gas constant, and B , n and Q are constants; the value of n is about 3.2, that of Q is 32 kcal/mole, and that of B is 7 x 10 24 if the stress is measured in bars and the strain rate in years -1 . At the higher stresses a third, accelerating stage of creep was observed; on the basis of the appearance and behaviour of sections cut from the specimens, this acceleration was attributed to recrystallization. The effect of changing the load during a test has also been studied; for large reductions creep recovery was observed. The results of these tests are discussed in connexion with previous work on metals and ice, and also with measurements of glacier flow.

ABSTRACT. This paper reviews the electrica l properties of snow a nd ice that are of importance in remote sensing using e lectrical devices. After a review of th e observed la borato r y behaviour of ice sa mples and the microscopic t h eory which has been advanced to explain this, the data on tempera te a nd polar glacier ice are compared with the labora tory data. Temperate glacier ice is generally rath er simil a r to laboratory ice, but certain relax a tion processes found in the laboratory are absent from the glacier ice. Polar ice, on the other hand, is consid erably different in its di electric behaviour from " pure" laboratory ice, or temperate glacier ice; in many ways it more rese mbles doped la bo ratory ice, d espite its variable, som etim es low, impurity con tent. It a lso resembles in behaviour ice produced by freezing supercooled water. Th e e lec trical behaviour of snow, a nd the a ttempts to account for this in te rm , of the b~h av i o ur of the ice and air componen ts, and a lso of the water com ponent in wet snow, a re next discussed. Fina ll y the implica tions o f this work for radioecho sounding of ice, radar re fl ec ti vity from wet a nd dry hydrome teors, d evices for d e te rmining the water content of snow, a nd resistivity surveys of glaciers a re discussed. RESUME. L es proprietes electriqlles de la Ileige et de la glace.Cet articl e passe en revue les proprie tes electriques de la neige et de la glace qui son t importantes dans les method es d e te ledetection utilisant des procedes electriques. Apres une revue des comportements observes au la boratoire d 'echantillons d e glace et d es theories a I'ech ell e microscopique avancees pour les expliquer, on compa r e les resultats sur glaciers temperes et pola ires a ceux obtenus en la boratoire. La g lace de glacier tempere est generalement assez sembl a bl e a la glace d e labor a toire, mais certa ins processus d e relaxation observes e n laboratoire ne se produisent pas dans la glace d e glacier. Les glaciers polaires, a u contraire, ont un com portement dielectrique tres difleren t d e cel ui de la glace " pure" de labora toire ou de la glace d e glacier tempe re; dans bien des cas, il s se rapprochent plus d e la glace " dopee" e n laboraloire, ma lgre leur te neur va ri a bl e, e t parfois faible, en impuretes. Ils ressembl e n t a uss i a la glace produite par congelation d 'eau surfondue. L e comportement e lectrique d e la neige, e t les te nta ti ves pour en rendre comp te a partir d e celui des composan ts glace et a ir ainsi que du composant ea u dans la neige mouillee, son t ensui te discutes. Finalement, on aborde les implicatio ns d e ce travail pour les sondages de la glace par rad io-echo, la re fl ee ti v ite a u rada r d es h yd rometeores humides e l secs, les procedes d e determination d e la teneur en eau d e la n e ige, et les e tudes d es glaciers par rts istivite. ZUSAMM ENFASSUNG. Die elektrischen EigCllschaflen von Se/mee ulld Eis. Diese Arbeit gibt e in en Oberblick liber die ele ktrischen Eigenschaften ...

ABSTRACT. This paper describes compression tests at -I ' 5° C. on blocks of ice containing many small crystals in random orientation. Results show that ice does not possess a constant coefficient of viscosity, but obeys a more complicated relation between compressive stress a and strain rate i. For the stress range 1'5-10 Kg. cm.-2 this relation is approximately of the form" =ko", where n is a constant equal to about 4. A method of preparing small cylindrical single crystals of ice of a desired orientation is also described.

ABSTRACT. This paper describes compression tests at -I ' 5° C. on blocks of ice containing many small crystals in random orientation. Results show that ice does not possess a constant coefficient of viscosity, but obeys a more complicated relation between compressive stress a and strain rate i. For the stress range 1'5-10 Kg. cm.-2 this relation is approximately of the form" =ko", where n is a constant equal to about 4. A method of preparing small cylindrical single crystals of ice of a desired orientation is also described.

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