504 THE ANTARCTIC MANUAL. 
rubbish, however, was concealed by the loose snow on the surface. I 
measured the height of the ice-ramparts in several places by carefully 
marking out a base-line on the frozen surface of the sea, and observing 
the angles of elevation with the sextant; the average height was about 
90 feet. Of course the icebergs formed in Robertson bay do not attain any- 
thing like the dimensions of those drifting up from farther south, where 
the glaciation is so much greater. On the lee side of the ice-tongues great 
piles of snow-drift were accumulated by the east-south-east winds, and 
heaped up almost on a level with the summit of the wall. The sea-ice 
around the extremities of the tongues was very little cracked or crushed 
together, thus indicating that the movement of the glaciers was not, 
at that time of the year, very considerable. 
The glaciers of the antarctic do not, I think, move rapidly at any 
time of the year. In this respect they are very different to those of 
Greenland, some of which, I believe, are the most rapid moving glaciers 
on the surface of the globe. No actual measurements on the rate of motion 
of the glaciers of South Victoria Land have been made, so that nothing 
positive respecting them can be advanced. Sharp detonations, however, 
were frequently heard, showing that there was some movement going 
on in the mass. 
The spot where we ultimately camped was a small islet, which has 
been named Duke of York island, and which is, perhaps, 3 miles in 
circumference, and surrounded by a glacier that nearly conceals its 
insularity. The geological formation consists of a greenish slatey rock 
of very fissile structure, which is on the whole intensely crumpled and 
plicated. Crystals of pyrites occurred disseminated throughout the forma- 
tion, in some places in great abundance. The pyrites appeared in small 
cubical perfectly opaque crystals, which, with reflected light, showed 
the characteristic brassy lustre of the mineral. These crystals appeared 
to yield but slowly to weathering, for generally the cubical crystal 
could be seen projecting still fresh from the stone, which had no 
doubt been long exposed to the atmosphere, and a small blow would, 
in many cases, loosen the entire crystal from the rock. The forma- 
tion was here and there traversed by thick veins and narrow 
threads of quartz, showing strong evidence of disturbance, and seemed 
to have been exposed to a powerful lateral pressure; this quartz 
contained bluish and rusty-coloured streaks. In the crevices of the 
slate rock a dark soft soapy substance something like graphite was 
found. In some places the stratification formed roads on the side of the 
mountain some 30 or 40 feet in width; in other places the greenish 
colour of the formation was changed to a dull brick-red, as if it had 
been under the influence of heat. Whether this is really caused by 
heat or is merely the ordinary effect. of weathering, I do not know ; 
I think the latter cause is the most probable. These red patches were 
conspicuous some miles away, and were exactly similar to the formation 
