L] GEOLOGICAL OBSERVATIONS 341 



which is 100 yards long and 200 feet high, exhibits columns about 

 twelve feet in diameter and between twenty and 200 feet in length. 

 There are occasional horizontal joints, but cup-and-ball structure 

 is not developed to any great extent. The sandstone appears to 

 rest upon the surface of this dolerite, but the junction of the two 

 could not be discovered. 



We have already seen that the mountains which separate the 

 North from the East Fork are capped by dolerite, and that another 

 sheet of dolerite, apparently arising at the western end, has flowed 

 over a surface of granite. This last feature appears to be again 

 developed in the Cathedral Rocks, for a black columnar rock is 

 separated from the granite by a very definite line. Therefore 

 dolerite probably helps to build the Cathedral Rocks as well as 

 other parts of the Royal Society Range. 



In Granite Harbour a dark rock lies unconformably upon the 

 surface of a light-coloured one, and as the lower rock was proved 

 to be granite, and boulders of dolerite were found on it, we may 

 very reasonably assume that here also a sheet of dolerite lies upon 

 an older mass of granite. 



A few additional notes on the basaltic rocks of Cape Adare may 

 be included here. It may be remarked that this Cape lies at the 

 foot of the gigantic mountain range and possesses horizontal sheets 

 of basalt, basaltic agglomerate and tuffs, and its rocks may there- 

 fore have some connection with the same rocks in Coulman Island 

 and the other islands off the coast. The sheets consist of both 

 olivine and hornblende bearing basalts which are occasionally cut 

 through by vertical dykes. 



This structure appears to be characteristic of the steep coast- 

 line between Cape Adare and Cape Jones, a distance of 150 miles. 

 This part of the coast is a cliff varying in height from 500 to 1,000 

 feet, and always shows layers arranged more or less horizontally, 

 making up the whole cliff. Low anticlines and synclines with east 

 and west axes, occur at intervals along this piece of coast, and 

 occasionally red bands could be distinguished which appear similar 

 to those on Coulman Island or Cape Adare. 



The Ice. 



The Sea-ice. — The term Sea ice is perhaps the most suitable for 

 all ice produced by the freezing of the sea, and it also draws a 

 distinction between this ice and that which has another origin. In 



