THE HIGHLAND BORDER ROCKS OF THE ABERFOYLE DISTRICT. 
209 
The Upper Series includes a fossiliferous limestone, and may be placed with 
confidence on a higher horizon in the Ordovician system. 
4. The igneous rocks, both lava-form and intrusive (including their metamorphosed 
representatives), which are associated with the Lower Series show certain affinities 
in mineralogical composition and in petrographical characters which lead to the con- 
clusion that they have been derived from the same magma. 
5. The hornblendic and chloritic schists are the result of the dynamic meta- 
morphism of hypabyssal and volcanic rocks along a belt where these rocks w r ere 
subjected to intense shearing. The metamorphosed sediments were affected by 
contact metamorphism prior to the dynamic metamorphism of the belt. 
6. The whole belt of Highland Border Rocks is affected by lines of crushing and 
dislocation running in the direction of the general strike of the beds. 
7. The age of the Leny Grits still remains an open question, and one on which 
further investigation is needed. But it is clear that a line or lines of dislocation 
separate these from the Highland Border Series. 
XIV. Acknowledgments. 
The area occupied by the Highland Border Rocks was mapped on the scale of 
six inches to a mile by Professor Jehu, who had the great advantage of having 
placed at his disposal by the late Dr C. T. Clough his field notes and the working 
copies of his map of the region. We wish to record here our indebtedness to 
Dr Clough not only for the assistance derived from perusal of his notes and maps, 
but also for the generous way in which he helped us from time to time in dis- 
cussing difficulties in the light of his intimate knowledge of the district and of the 
problems involved. 
The main boundary lines in the accompanying map coincide generally with those 
drawn by Dr Clough. The chief modifications are as follows : (a) the interpreta- 
tion of the northern boundary of the hornblende-schist complex as a fault ; ( b ) the 
mapping of a zone of spilitic lavas in the Gualann area, in part included by Dr 
Clough in the hornblende-schist complex ; (c) the recognition of the breccias, which 
we regard as the basement beds of the Margie Series, on both sides of the main 
black shale and chert ridge ; ( d ) numerous modifications of the boundary lines 
between the Black Shale and Chert Series and the Margie Series ; (e) alteration of 
the position of the southern boundary line of the Leny Grits (particularly opposite 
Dungarrow) and its interpretation as a line or lines of dislocation : we understand 
that latterly Dr Clough adopted this interpretation for certain sections. 
So far as we have been able to ascertain from his published and unpublished 
writings, our conclusions are different from those reached by Dr Clough in the 
following main particulars : (a) the definite separation of the Highland Border 
Rocks into a Lower and an Upper Series separated by an unconformity ; (b) the 
discovery of fossils other than Radiolaria in the Lower (Black Shale and Chert) 
