MOUNT EREBUS 213 



fumaroles were iii active eruption at the time of our visit on March 9, 10, 1908, 

 and merely a very gentle current of air was issuing from them. At times, when the 

 steam cloud over Erebus was develojjed on a larger scale than usual, it seemed to us 

 that an outburst took place from some of these fumaroles, and no doubt at such a 

 time hot steam and various vapours, especially sulphurous, would be given off. The 

 shapes of the raised mounds around the mouths of the fumaroles was most weird 

 and fantastic, some resembling pinnacles or minarets, others being dome-shaped 

 like gigantic beehives. Many recalled the shape of the ventilating cowls used on 

 the decks of ships. Their height was mostly from 10 to 20 feet. 



In ascending the gently-inclined filled-up floor of this second crater we reached, 

 at an altitude of about 12,000 feet, what appeared to be a small parasitic cone 

 within the old crater. Fragments of lava and felspar crystals in its vicinity were 

 covered in places with sulphur. The ice, too, in patches near here was of a lemon- 

 yellow hue, owing to the admixture with it of sulphur. Here we saw that the 

 covering of snow became thinner, vmtil it almost entirely disappeared, being replaced 

 by a surface formed of crystals of anorthoclase felspar from half an inch to 4 inches 

 in length. These were mostly very perfectly formed, but many showed signs of 

 their angles and edges having been considerably abraded through attrition. Here 

 and there one noticed a small quantity of volcanic glass adhering to the crystals, 

 and amongst them were numerous fragments of pumice, with the large ^^orphyritic 

 anorthoclase crystals entangled in it. Evidently these crystals had formed at a 

 considerable depth below the surface in the volcanic chimney, or reservou-, beneath 

 it, and when the magma, charged with these porphyritic crystals and steam, reached 

 the surface, the glassy magma had been blown, through the force of the steam 

 explosions, into the form of impalpable dust, thus setting free the porphyritic 

 crystals, Avhich must thus, during an eruption of Erebus, form a continuous hail- 

 storm for some distance around the crater. The direction in which the maximum 

 fall of these crystals takes place is controlled by that of the prevalent winds at 

 the time. 



The character and shape of these crystals, as well as of the pumice in which 

 some of them are included, is shown on the accompanying plates (Plates LXIV. and 

 LXV.). 



It may be mentioned that on the evening of March 9, at 8.30 P.M., at the rim of 

 the second crater of Erebus, at an altitude of about 11,350 feet, light snow fell. 

 The sky at the time was quite thickly overcast. The fact that snow actually falls 

 over the summit of Erebus is obviously of some meteorological interest. Just 

 previous to the snowfall a perfect sea of dense cumulus cloud had been seen by us 

 rolling inland from Cape Bird to at least as far south as Cape Royds, and was 

 surging against the foothills of the great cone of this second crater, at an altitude 

 of about 6000 feet above sea-level. It is possible that this northerly wind, bringing 

 in with it the cumulus snow-clouds from off Ross Sea, climbed the slopes of this 



