Geological Relations of the East of Ireland. 145 
through mica slate. Somewhat similar relations may also be ob- 
served in the line of Lough Tay and Lough Dan. 
The rocks on the eastern bank of the stream in Glenmacanass, 
below the waterfall, being cut through by the military road, we 
perceive that the mica slate contains frequent beds of quartz, from a 
few inches to two and three feet wide, and also beds of granite two 
and three feet in thickness, interstratified with the mica slate. One 
of these beds of granite contains a considerable proportion of 
disseminated schorl. These rocks dip 20° to 25 p toward the south- 
east. 
§ 27. The body of mica slate, on the western bank opposite, 
demanded farther research. I pursued its course, which led me to 
Tonelagee. This mountain is the most elevated point of the range 
which separates Glenmacanass from Glenasane. It stands on the 
northern side of the pass, called Wicklow Gap, and fronts Coma- 
derry range on the south, with its granite precipices overhanging 
Loughnahanagan. The range of Tonelagee is composed of granite 
down to the head of Glenasane and the lower part of Glenmacanass; 
but to the east of this line is a hollow valley, on the north side of 
which a ridge extends from Tonelagee to Glenmacanass, forming the 
body of mica slate in question, and the southern barrier of Lough 
Ouler. 
Above this lake, the brow of Tonelagee exhibits bold precipices 
from four hundred to five hundred feet high, and in these an 
arrangement is displayed that is well deserving of attention. The 
northern portion is wholly composed of granite, and the southern is 
similarly constituted, down to the arm which extends to Glen- 
macanass, which consists of mica slate, as already stated. In the 
interval, however, between the northern and southern parts of the 
precipice, is a body of mica slate about two hundred yards wide, 
Vol. V. 
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