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AURORA AUSTRALIS. revealed to us in all its vast extent and depth.

Mawson’s measurements made the depth 900 feet, and the greatest width about half a mile. There were evidently at least three well-like openings at the bottom of the caldron, and it was from these that the steam explosions proceeded. Near the south-west portion of the crater, there was an immense rift in the rim perhaps 300 to 400 feet deep. The crater wall opposite to the one at the top of which we were standing, presented features of special interest. Beds of dark pumiceous lava, or pumice alternated with white zones of snow; there was no direct evidence that the snow was interbedded with the lava, though it is possible that such may have been the case. From the top of one of the thickest of the lava, or pumice beds, just where it touched a belt of snow, there rose scores of small steam jets, all in a row; they were too numerous and too close together to have been each an independant [sic] fumarole. The appearance was rather suggestive: of the snow being converted into steam by the heat of the layer of rock immediately below it. While at the crater’s edge we made a boiling point determination with the hypsometer, but the result was not so satisfactory as that made earlier in the morning at our Camp. As the result of averaging aneroid levels, to-