FELSPAR CRYSTALS 



projecting ledge of dark rock is uncertain. It is evident 

 from the mineralogical character of the recently erupted 

 pumice of the active crater that Erebus is still producing 

 that rare type of lava known as kenyte. Two features 

 on the geology of Erebus which are specially distinctive 

 are the vast quantities of large and perfect felspar 

 crystals, and the ice fumaroles. The crystals are from 

 two to three inches in length. Many of them have had 

 their angles and edges slightly rounded by attrition, 

 through clashing against one another when they were 

 originally projected from the funnel of the volcano, but 

 numbers of them are beautifully perfect. The fluid lava 

 which once surrounded them has been blown away in the 

 form of fine dust by the force of steam explosions, and 

 the crystals have been left behind intact. 



" The ice fumaroles are specially remarkable. About 

 fifty of these were visible to us on the track which we 

 followed to and from the crater, and doubtless there 

 were numbers that we did not see. These unique 

 ice-mounds have resulted from the condensation of 

 vapour around the orifices of the fumaroles. It is 

 only under conditions of very low temperature that such 

 structures could exist. No structures like them are known 

 in any other part of the world. 



" It would be hard to overestimate the scientific 

 importance of knowledge of the meteorological con- 

 ditions obtaining at Erebus. Erebus is the Pisgah of 

 the meteorologist. The details of the phenomena 

 observed there will, of course, be given in the meteoro- 

 logical memoirs of this expedition, but they are too 

 bulky to quote here. Mention, however, may be made 

 of four phenomena which specially impressed them- 

 selves upon us during our ascent of Erebus. In the 

 first place we noticed that the whole of the snow-field 

 lying within the rim of the second crater is strongly 



195 



