12 W. R. BROWNE. 
Again, as further evidence, as has been stated above, at 
Bunyan the Ordovician slates are silicified for some distance 
out from their contact with the white gneiss. Now this. 
white gneiss is closely associated with the blue gneiss, and 
this would go to show that. the gneiss is later than these 
slates. 
It has been urged that strike faulting could have thrown 
down the Ordovician slates against the Pre-Cambrian 
schists, but in this case the problem of the transitional 
phyllites becomes insistent of solution. Of course it may 
be argued that, as no definite junction between Silurian 
and Ordovician can be found, any original unconformity 
between Ordovician and older formations would likewise 
be obliterated. But on the other hand the Ordovician 
and Silurian can be separated on fossil evidence, whereas 
there is nothing but gradual change of lithological char- 
acters to differentiate the schists from the slates. 
So far as I can interpret it, the evidence available would 
point to the fact that we are dealing with an area which 
has been affected by both regional and contact metamor- 
phism. The gneisses have been intruded successively and 
crystallized under conditions of great pressure; the schists. 
would then be caused by contact metamorphism of the 
slates in the vicinity of the gneissic intrusions, the intensity 
of the metamorphism gradually diminishing outwards. It. 
is plain that there is a much greater extent of gneiss than 
indicated by the outcrops, and in such case the underground 
extension would go to the west principally. The suggested 
broad relations between the metamorphic rocks and the 
other formations of the area are shown in Fig. 1. 
Iam quite aware that the hypothesis here advanced | 
raises serious difficulties, but at the same time it is to be — 
understood that the evidence so far gathered is by no means. 
regarded as conclusive; nothing at all final can as yet be 
oo Phat ti ge 
