202 W. R. BROWNE. 
away from the syenite, gradually becoming less and less 
plutonic in character. The actual contact of the syenite 
with the older rocks is covered over by basalt. or alluvium, 
so it was not possible to obtain any information as to the 
nature and amount of the contact metamorphism or the 
form of the intrusion. 
Geological age of the igneous intrusions.—There are no 
means of determining with exactitude the geological age 
of all these intrusions, nor indeed is there any direct evid- 
ence to show that they are genetically connected, or even 
contemporaneous with each other. It will be observed on 
referring to the map that the syenite is a long way away, 
and quite isolated from the granite, and that the porphyries 
are far removed from both. : 
With regard to these porphyries, if they all belong to the 
Same series they must be Post-Silurian, but if not, then 
some may be as old as the Ordovician. Very much 
mylonized porpbyries, hardly recognizable as such, occur 
in among the Ordovician slates at and north of Bunyan, 
and it is possible that here they represent contemporaneous 
submarine sheets interbedded with, and subsequently tilted 
and compressed along with, the original sediments. On 
the other hand, others of the porphyries have all the appear- 
ance of intrusions, fragments of the intruded slates being 
included, and slight alteration of the surrounding rocks 
being produced. The form of the outcrop too, in many 
cases, suggests a tapering sheet or sill. The intruded 
formations in these cases embracing Silurian beds, the 
porphyry must be of laterage. Some of the quartz-porphyry, 
since it is relatively unshattered, must have been injected 
after the folding and compression had practically ceased. 
The granite and the syenite are both clearly later than 
Silurian, as they have been subjected to strain only toa 
slight extent. The granite along its marginal portions and 
