218 GENERAL GEOLOGY 



absolutely certain as to whether this steana was coming exactly from that spot. It 

 did not appear to be connected with the active crater. 



On July 15, 1908, there was again a very strong glow over Erebus, and again 

 on the 16th and 17th, also on the 19th and 27th July. 



On August 1, 1908, thei-e were signs of a strong steam eruption at Erebus. On 

 August 25th there was a remarkably bright glow over Erebus from about 10 p.m. 

 till past midnight. On September 8th, at 8.5 p.m., a remarkable outburst of 

 the Cape Bird fumarole was witnessed by Murray and Marshall. According to 

 Murray's estimate, this eruption must have carried the steam up several thousands 

 of feet, as, measuring to the jioint indicated as its summit level, its angle of eleva- 

 tion was fully 5 J degrees as seen from Cape Royds. This would probably give a 

 minimum height of about 11,000 feet. 



Caioe Bird. A landing was effected here by Lieutenant Macintosh and 

 McGiUan on January 3, 1909, after their adventurous journey, during which they had 

 to abandon theii" tent and the mail bags. The Ninirod put in here on February 11, 

 1909, when Mawson landed and obtained a number of geological specimens, mostly 

 loose pieces of rock, and we obtained the photographs reproduced on Plate LXIX. 



These show at least one well-marked volcanic cone at the spot on the coast 

 shown on the plan. 



In his description of the specimens from this locality Dr. Jensen describes these 

 rocks as being intimately related to those of Erebus, being alkaline in facies. " TheLr 

 distinguishing feature in all varieties," Dr. Jensen reports, " is the abundance of 

 brown basaltic hornblende, and alteration products after this mineral." The chief 

 rocks he describes as strongly alkaline trachytes, kulaites, and sub-alkaline basalts 

 and dolerites, amongst which latter he distinguishes olivine basanites, alkaline 

 dolerite, and limburgitic dolerite. 



We can now pass on to the parasitic cones and other evidences of vulcanism in 

 the neighbourhood of Cape Royds and Cape Barne. 



Cape Royds. Cape Royds is probably situated near an independent point of 

 eruption of the nature of a parasitic cone, but as the result of a long period of 

 denudation, chiefly effected during the maximum glaciation, its true structure 

 is largely obscured by extensive patches of morainic material. It is obvious, 

 nevertheless, that Cape Royds is traversed by a network of volcanic dykes inter- 

 secting some of the older kenyte lavas. At Flagstaff" Point, at the landing 

 place on its south side, distinct stratification is noticeable in the volcanic rocks, the 

 dip being somewhat steeply seawards. Here and there some resistant dykes stand 

 out prominently, such as the one at the Penguin Rookery, and that which divides up 

 Blue Lake. The principal type of rock at Cape Royds is a highly-jointed alkaline 

 basic lava, rendered porphyritic by anorthoclase, which Dr. G. T. Prior identifies as a 

 kenyte identical in character and composition with that of Mount Kenya in Central 

 Africa. The kenyte is black, and in places has a very glassy base. The felspars are 



