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3. The number of detached blocks of naujaite imbedded in 
the upper part of the lujavrite mass is very large, and nearly 
all lie undisturbed with their partings parallel to those of the 
overlying unbroken naujaite mass. In a ‘stoping breccia’ rela- 
tively few roof blocks would fail to sink, and ‘the sides of the 
different blocks would in sinking take up very various posi- 
tions. 
The absence of stoping action may evidently be referred to 
the low specific gravity of naujaite, as compared with that of 
lujavrite. The specific gravity of naujaite is 2°5, and of lujavrite 
2°8. At the time of formation of the breccia the lujavrite magma 
was of course lighter than 2°8, but lujavrite magma was probably 
rather viscous, and that it had already started to crystallize has 
been proved by the flow structure. It is not, therefore, probable 
that the specific gravity at the time of intrusion should have 
been so much lower than 2°8 that naujaite blocks could sink. 
The breccia zone is, thus, assumed to have been produced 
by the same movements which gave rise to the concave form 
of the sheets, viz. the unequal subsidence of the mass. In 
seeking for the explanation of this local subsidence which, as 
we have seen, must have occurred during the latest stages of 
the consolidation of the batholite, two possibilities are to be 
considered: either, the batholitic chamber at the time of the 
subsidence may have communicated with more deep-seated re- 
servoirs, or, it may have been cut off from communications of 
this kind. If the batholitic chamber were open, the most simple 
explanation is that the magma has sunk. If closed, the un- 
known substratum of the lujavrite may perhaps have remained 
fast, and the subsidence may have been caused by the diminu- 
tion of volume. of the lujavrite, as it crystallized and became 
solid. As we do not know the thickness of the lujavrite mass 
it must remain undecided, whether the latter hypothesis suffices 
to explain the subsidence or not. 
Mutual relation of the stratified and the unstratified parts 
