293 
In the preceding chapters two batholites have been de- 
scribed. One of them — the large Igaliko batholite — is in 
a state of preservation which is very unfavourable to a study 
of any geological features which might lead to an interpreta- 
tion of the mechanism of intrusion. In this case the original 
cover of the batholite has been entirely denuded, the junction 
with the country rock is only exposed in a few sections of 
inconsiderable height, and it is not possible to arrive at any 
definite conclusion as to the mode of formation of the batholite. 
It deserves mention that the position of the sandstone at Nar- 
sarsuk and Iganek (more than 1700 meters below the near top 
of the batholite) favours the supposition that invasion here has 
taken place under conditions quite like those which controlled 
the invasion of the batholite next to be mentioned. 
The Ilimausak batholite is exceedingly well exposed for an 
inquiry into the mechanism of intrusior. The original cover is 
partly preserved, and junctions with the country rocks are dis- 
closed in numerous natural sections from sea level to an alti- 
tude of more than 1100 meters. 
Form and boundaries of the Ilimausak batholite. -— The 
general features of the batholite as to shape and contact rela- 
tion will appear from the sections given in Fig. 27 (see also Plate 
IM, V, and VI). The plan of the mass is a rude ellipse, the. 
maximum diameter being about 20 kilometers while the breadth 
is less than 15 kilometers. The boundaries are of two kinds: in 
some places they are more or less parallel to the stratification 
of the invaded rocks, while in others they are distinctly trans- 
gressive. Contact surfaces of the former kind are found in the 
two southernmost peaks of Ilimausak. There erosion has left 
two outliers of the cover resting horizontally upon the Plutonic 
rocks. On closer inspection this contact plane proves very 
irregular: but on the whole it is parallel to the stratification. 
At the periphery of the batholite the boundaries are transgres- 
sive and often vertical. In all cases the contact proves to be 
