317 
exist. Even in cases where magmatic stoping can be neglected, 
the consolidation of abyssal rocks may have taken place much 
later than their intrusion. With batholites in which the con- 
tact relations are largely determined by the effects of stoping, 
the contact phenomena will depend rather upon the final 
stages of the process, than upon the original sequence of in- 
trusion. 
For this reason the magma reservoirs from which superti- 
cial lavas have originated may present themselves as apparently 
later intrusions into their own lavas (p. 305), and for the same 
reason the oft-discussed regular sequence of abyssal rocks 
obeying the ‘rule of decreasing basicity’, is in most cases 
simply a consequence of the fact, that basic magmas as a rule 
crystallize at a higher temperature than acid magmas, and is not 
necessarily an expression of the original sequence of intrusion. 
The ‘rule of decreasing basicity’ is in fact essentially a rule of 
decreasing temperature of consolidation. 
We may express the above statement from another point 
of view thus: — when the contact relations of abyssal rocks 
indicate a sequence of consolidation which agrees with the rule 
of decreasing temperature of consolidation, the evidence is in- 
sufficient to settle the question of the original sequence of in- 
trusion; but when the contact relations are at variance with that 
rule (e. g. gabbro veining granite) we may conclude that they 
express not only the sequence of consolidation, but also the se- 
quence of intrusion. 
The Paleozoic abyssal rocks in the south of Greenland 
agree with the rule of succession according to decreasing temp- 
erature of consolidation (gabbro — syenite — nepheline-syenite 
and granite). This fact in connection with the scarcity of basic 
dykes cutting the acid and intermediate batholites seems to show 
that all belong to one uninterrupted cycle of igneous activity. 
