i 82 transactions—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
dipping again at angles of from 50 to 6o degrees to the north-west, and 
evidently conformably succeeding the underlying and less altered 
beds. These again are succeeded by massive beds of grit and cono-lo- 
merate, with zones of phyllites, as seen on the shores of Loch Lubnaig, 
passing eventually upwards into the mica-schists, quartz-schists, and 
limestones of Balquhidder and Glen Dochart, and showing, so far as 
we have been able to observe, no evidence of any stratigraphical 
break. ° 
In conclusion, the structure, age, and relationships of this mar¬ 
ginal belt of rocks seen in Highland Perthshire must still remain an 
open question. For the reasons we have already discussed we are 
still unable to accept Nicol’s theory that the true position of this belt 
of arenaceous and argillaceous rocks is that seen in the south-western 
part of the mountain chain, while that shown in Perthshire is owinc^ 
to faulting and overthrust. Could this be definitely shown to be the 
case, then we could understand the position of these unaltered beds 
in this marginal belt. On the other hand it would seem from the 
Government Reports that Sir A. Geikie would prefer to separate out 
these less altered beds from the main mass of the grits and phyllites, 
relegating the latter to the crystalline rocks of the Highlands. But 
he is unable to find any line of demarcation between the two. In the 
meantime, until further evidence is forthcoming, we are inclined to 
look upon this marginal belt of grits and phyllites, with the less 
altered beds of shale and limestone, as forming one stratigraphical 
group, conformably underlying and older than the schists and lime¬ 
stones of the interior. Nor do we think that the less altered appear¬ 
ance of certain of the beds militates against this view, as the amount 
of metamorphism varies exceedingly along the line of strike. 
Let us now proceed to a consideration of some of the more 
recent advances which have been made in the study of those altered 
basic rocks known as epidiorites and hornblende schists. It is not 
necessary that we should here enter into any of the earlier opinions 
held concerning these rocks. Of all the schists found in the High¬ 
lands, these hornblende schists seemed to lend the most support to 
the old view that they had been precipitated from the thermal waters 
of some primeval ocean, the presence of hornblende, garnet, and other 
minerals in a highly cr5^stalline condition seeming to support this 
view of the origin of these rocks. But from the advance of our 
knowledge concerning the changes which have been produced upon 
both igneous and aqueous rocks by dynamic metamorphism, it is 
now well known that most of these schists were originally ordinary 
sediments, and even igneous rocks, upon which a foliated or schistose 
structure has subsequently been superinduced by the straining and 
shearing of the rocks. 
