53 
masses of intrusive igneous rock as those at the base of the series ; 
the latter stretch between the St. John’s Quartz Felsite and the 
Ennerdale Syenitic Granite, and the former between the Shap 
Granite and the southern part of the Eskdale Granite; and it is 
highly probable that the irruption of the igneous masses, in both 
- cases, may have assisted in producing slaty cleavage in the beds 
which lie between them. A line drawn on the map from Elter- 
water to the southern end of Eel Crags marks the centre of the 
area in which slaty cleavage occurs in both the upper and lower 
beds ; and similar lines drawn from Walna Scar to Scarf Gap, and 
from Cawdale Moor to Lodore waterfall, mark the south-western 
and north-eastern boundaries of that area. Extending these lines 
forward beyond the points named, they form a junction at Green- 
banks, near Cockermouth, and enclose a triangular area having for 
its base the outcrop of the Coniston Limestone, and its apex the 
farm of Greenbanks. This triangle, therefore, encloses the rocks 
that were subjected to the maximum of pressure during the earth 
movements by which cleavage was caused. 
APPENDIX. 
On the Structure of some Volcanic Ash from the Borrowdale Series, 
by Professor Bonney, D.Sc, LL.D., F-G.S., FR.S. 
No. 1 and the coarser part of the other slides consist of small 
mineral and rock fragments, angular and subangular in outline, 
and seldom exceeding ‘03” in longest diameter, commonly rather 
less. The majority of the mineral fragments were evidently felspar. 
All are more or less altered, being replaced by a filmy mineral 
which gives bright tints with crossed nicols and by thin lines of viri- 
dite (this may result from infiltration). A minute description of 
the changes is needless, for there is nothing unusual. A few 
fragments are wholly or almost wholly replaced by viridite; these 
