THE HEART OF THE ANTARCTIC 



They steered for some of the remarkable mounds 

 already mentioned, and when the nearest was reached 

 and examined, they noticed some curious hollows, 

 like partly roofed-in drains, running towards the 

 mound. Pushing on slowly, they reached eventually 

 a small parasitic cone, about 1000 ft. above the level 

 of their camp and over a mile distant from it. Sticking 

 out from under the snow were lumps of lava, large 

 felspar crystals, from one to three inches in length, 

 and fragments of pumice; both felspar and pumice 

 were in many cases coated with sulphur. Having 

 made as complete an examination as time permitted, 

 they started to return to camp, no longer roped 

 together, as they had not met any definite crevasses 

 on their way out. They directed their steps towards 

 one of the ice mounds, which bore a whimsical re- 

 semblance to a lion couchant and from which smoke 

 appeared to be issuing. To the Professor the origin 

 of these peculiar structures was now no longer a 

 mystery, for he recognised that they were the outward 

 and visible signs of fumaroles. In ordinary climates, 

 a fumarole, or volcanic vapour-well, may be detected 

 by the thin cloud of steam above it, and usually one 

 can at once feel the warmth by passing one's hand 

 into the vapour column, but in the rigour of the Ant- 

 arctic climate the fumaroles of Erebus have their 

 vapour turned into ice as soon as it reaches the surface 

 of the snow-plain. Thus ice mounds, somewhat similar 

 in shape to the sinter mounds formed by the geysers 

 of New Zealand, of Iceland, and of Yellowstone Park, 

 are built up round the orifices of the fumaroles of Erebus. 

 Whilst exploring one of these fumaroles, Mackay fell 

 suddenly up to his thighs into one of its concealed con- 

 duits, and only saved himself from falling in deeper still 



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