1903 - 4 .] Mr J. G. Goodchild on Intrusive Bocks. 
213 
case cited is a perfectly typical one so far as the relation of veins 
of granite to the country rock is concerned. There is not the 
slightest evidence of any disruption of the rock invaded by the 
granite ; but, on the contrary, it is perfectly clear that there has 
been, in these cases also, a concurrent removal of the country 
rock going on while the introduction of the material that after- 
wards consolidated as granite was in progress. But before passing 
on to consider in more detail the mode of attack followed by these 
acid intrusive rocks, I may perhaps be permitted to repeat the 
statement that the acid and subacid dykes (of Devonian age) which 
traverse the Ordovician and Silurian Bocks of the Kendal and 
Sedbergh districts, referred to at the commencement of this paper, 
behave in precisely the same manner as the granite veins just cited. 
The lamprophyre occurring, at Swindale Beck, Knock, near 
Appleby, which was figured in Teall’s British Petrography as a 
typical minette, certainly eats its way into the country rock 
in the manner already described in so many other cases. I 
have figured it in plan in the Geological Survey Memoir on 
Sheet 102 S.W., to which the reader may be referred. 
Lastly, so far as the mode of occurrence of dykes is concerned, 
the well-known pitchstone of Corriegills Shore, on the east coast 
of Arran, sends finger-like ramifications into the enclosing rock, 
some of which are clearly seen to terminate against the Bunter 
Sandstone around it in the manner already described in connection 
with the dykes of basalt. One specimen showing this mode of 
■occurrence of the pitchstone is exhibited in the Scottish Collection 
already referred to. 
Leaving this part of the subject for the present, it may be 
remarked here that there are some singular features about basic 
dykes in general which may be noticed in the present connection. 
These are (1) the very small proportion which their width bears to 
their length (and usually to their depth) p(2) their wonderful uni- 
formity of composition as a whole, wdiich they maintain throughout 
the whole of their extent ; (3) the remarkable parallelism of their 
enclosing walls as a rule ; (4) the fact that the dykes most extensive 
in their range are those in which lime-soda felspars predominate. 
Lurthermore, the mode of occurrence of a basic dyke suggests 
that the attacking surface formed by its magma was limited to its 
