The "erratics" comprised a great variety of metamorphic and igneous rocks, and, on a more limited scale, sedimentary types. Amongst the latter were sandstones, slates, shales and limestones.
Apart from the moraines, the rock exposed in situ was mainly a uniform type of gneiss, crumpled and folded, showing all the signs of great antiquity—pre-Cambrian, in the geological phrase. Relieving the grey sheen of the gneiss were dark bands of schist which tracked about in an irregular manner. Sporadic quartz veins here and there showed a light tint. They were specially interesting, for they carried some less common minerals such as beryl, tourmaline, garnet, coarse mica and ores of iron, copper and molybdenum. The ores were present in small quantities, but gave promise of larger bodies in the vicinity and indicated the probability of mineral wealth beneath the continental ice-cap.
CHAPTER VII THE BLIZZARD
The equinox arrived, and the only indication of settled weather was a more marked regularity in the winds. Nothing like it had been reported from any part of the world. Any trace of elation we may have felt at this meteorological discovery could not compensate for the ever-present discomforts of life. Day after day the wind fluctuated between a gale and a hurricane. Overcast skies of heavy nimbus cloud were the rule and the air was continually charged with drifting snow.
Lulls of a singular nature occasionally relieved the monotony. During these visitations the sequence of events could almost be predicted; indeed, they would often occur at the same time on several succeeding days.
On March 19 the first well-marked lull intervened at the height of a gale. On that day the wind, which had been blowing with great force during the morning, commenced to subside rapidly just after noon. Towards evening, the air about the Hut was quite still except for gusts from the north and rather frequent "whirlies."
This was the name adopted for whirlwinds of a few yards to a hundred yards or more in diameter which came to be regarded as peculiar to the country. Similar disturbances have been observed in every part of the world, but seldom possessed of the same violence and regularity as is the case in Adelie Land.
The whirlies tracked about in a most irregular manner and woe betide any light object which came in their path. The velocity of the wind in the rotating column being very great, a corresponding lifting power was imparted to it. As an illustration of this force, it may be mentioned that the lid of the air-tractor case had been left lying on the snow near the Hut. It weighed more than three hundredweights, yet it was whisked into the air one morning and dropped fifty yards away in a north-easterly direction. An hour afterwards it was picked up again and returned near its original position, this time striking the rocks with such force that part of it was shivered to pieces. Webb and Stillwell watched the last proceeding at a respectful distance.
Again, the radius of activity of these whirlies was strictly limited; objects directly in their path only being disturbed. For instance, Laseron one day was skinning at one end of a seal and remained in perfect calm, while McLean, at the other extremity, was on the edge of a furious vortex.