A CONTRIBUTION TO THE STUDY OF ICE-STRUCTURES 19 



Interesting observations on ice forms developed under varying conditions were 

 made within the precincts of the Hut itself. In explanation of subsequent statements, 

 brief mention of the plan of the Hut is necessary. The Hut was entered by an outer 

 door, then along a short vestibule and through an inner door. The Low-temperature 

 Laboratory was a small, tightly enclosed room outside the main room of the Hut, and was 

 entered by a door in one of the walls of the vestibule. From the Low-temperature 

 Laboratory a scramble on hands and knees under the floor of the vestibule brought 

 one to Wild's Store, another well-enclosed adjunct to the Hut. The cooking-range, the 

 only source of heat, was at the end of the Hut remote from the entrance door. Near 

 the stove the temperature would be well above 32° F. and it fell off regularly en route 

 to Wild's Store. The journey to the latter was quite a long and devious one, and along 

 the path there was usually a slight current of air, particularly when the inside door of 

 the Hut was opened. The average winter temperature in Wild's Store ranged from 

 -20° F. to -30° F. As giving some idea of the conditions in the Low-temperature 

 Laboratory, it may be mentioned that on one occasion when the outside temperature 

 was -20° F. that in the Low-temperature Laboratory was -6° F. 



Moisture rising from the cooking and from our breath kept the air in the Hut fairly 

 well saturated. Much of this was continually depositing as a fuzzy coating in odd 

 corners where low temperatures prevailed, particularly on the inside of the inside door. 

 All such deposits were, however, of little interest, because they never remained long 

 enough to develop pronounced structure before being destroyed by partial thaw as a 

 result of the wide range of temperature experienced within the Hut. 



(a) Crystallisations from Concentrated Vapour. 



In the vestibule snowy growths, usually of a fluffy character, formed on the walls 

 and ceiling so rapidly that it required to be scraped out at very frequent intervals. Thus 

 was exemplified crystallisation from a copious supply of over-saturated atmosphere, at 

 temperatures not greatly below freezing-point. The draught causing rapid carriage 

 of the vapour was certainly a factor in determining its fluffy character. 



Similar conditions pertained in the stable, where the breath from the ponies poured 

 forth a copious vapour which froze in beautiful fern -like forms attached to the ceiling and 

 on hanging objects (see Plate V, Fig. 1). 



The flocculent snow, in delicate flakes, which falls during the Antarctic summer, 

 and more rarely at other times during the year near the sea -board, is of this class. 



(b) Crystallisations from an Attenuated Vapour. 



At lower temperatures, even at 100 per cent, humidity, the vapour is attenuated 

 and the precipitation is modified, as exemplified by the formation which appeared in 

 the Low-temperature Laboratory (see Plate VI, Fig. 2). Deposition 

 was much slower there than in the vestibule. However, a coating 

 of blade -like forms, standing perpendicular to the walls and ceiling, 

 gradually developed (see Plate VI, Fig. 1). In this formation each 

 blade is a composite basal plate built up of innumerable, almost 

 microscopic scales, each with trigonal symmetry as shown in the 

 sketch (Fig. 6). 



These small units remind one of forms which compose the FlG 6 jce-Scale with 

 precipitation during certain Antarctic winter snowfalls. Trigonal Symmetry 



Reference to a form of platy crystallisation has been made by 

 David and Priestley (Vol. I, p. 19). The details there mentioned are not quite clear, 

 however, and something more may be added. On that occasion, as we sledged along 

 over the hard neve surface of the plateau on a bright sunny day, a carpet of ice-blades 



