158 TRANSACTIONS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
additional evidence from Scotland. In the Pass of Killiecrankie 
dioritic dykes more or less schistose are frequent, some of which 
present interesting resemblances to certain of these Alpine horn¬ 
blende schists. The rocks can be examined hi situ close to the 
Garry and occur as boulders in its channel. They are more or less 
foliated, evidently sometimes containing biotite, and not unfrequently 
red-garnet. Occasionally the former presence of a porphyritic felspar 
is indicated by white spots. In other parts of the same mass garnets 
are abundant (I have long suspected that most eclogites are diorites 
in which garnet has taken the place of felspar). I have examined 
microscopically one of the less foliated examples from a dyke above 
the bridge in the village and the most foliated one from a boulder. 
Both, especially the latter, strikingly correspond with some of the 
rocks described in this paper, the hornblende occurring in dark green 
prisms with enclosures evidently of a later date than that of the 
principal crushing—the biotite being newer than the hornblende and 
sometimes suggesting pseudomorphic replacement, and the garnets 
being anterior to the crushing.” 
We have here cited this foot-note of Professor Bonney’s for the 
purpose of calling attention to his opinion that these rocks were origi¬ 
nally intruded amongst the clastic rocks in the form, of dykes. The 
great difficulty in exactly determining the true relationships of these 
rocks to those into which they have been intruded is owing to the 
amount of subsequent shearing and rolling out to which they have 
been subjected, so that the original relationships of the intrusive rock 
has been more or less obscured. Supposing they had been intruded 
as dykes, it is not difficult to conceive how they could be so stretched 
and rolled out along the line of shear as to become apparently almost 
included between the lines of bedding or foliation of the clastic 
schists. In the bed of the Garry the extreme tenuity of the masses 
of these hornblende schists would, we think, rather tend to favour 
their fissure or dyke origin. This view might well be held when we 
compare the size of these masses in the Garry with such an un¬ 
doubted sill as that which underlies the I.och Tay limestone, and 
which has been estimated at five hundred feet in thickness. 
The geological structure of the surrounding country is somewhat 
monotonous, presenting extensive zones of mica schist, quartz schist, 
and dark graphitic sericite-schist, the whole dipping at high angles 
towards the north-west. In the Pass of Killiecrankie the rocks 
become more arenaceous, and dip at high angles. The black gra¬ 
phitic schist of Ben Vrackie may probably belong to our upper 
argillaceous zone, and in that case it is the equivalent of similar 
rocks seen at Easdale, Oban, Ben Lawers, and Glenshee.* 
* Geological Magazine, 1896, p. 167. 
