A HISTORY OF CUMBERLAND 
Of the very interesting suite of minerals found as a result of the 
contact-metamorphism of limestones, such as Phlogopite, Diopside, 
Tremotite, Wollastonite, Garnet, Idocrase, Sphene, Graphite, and Pyr- 
rholite,no good examples have yet been detected actually in Cumberland, 
although they occur within a short distance of the county boundary. 
Contact-metamorphism has produced marked effect upon the vol- 
canic rocks, as already mentioned, and has given rise to some interesting 
minerals. Garnets occur here and there under these circumstances, 
chiefly in tuffs which had undergone a certain amount of decomposition 
prior to the intrusion of the eruptive masses with which the meta- 
morphism is associated. Epidote is a common alteration-product of 
rocks with this history. In many cases in Cumberland it may represent 
one of the ‘Green Earths’ (Celedonite, Delessite, Saponite, etc.), which 
were originally derived from some ferro-magnesian minerals in the rocks 
affected, chiefly by the action of percolating water derived from the sur- 
face. These ‘Green Earths’ are very prone to change into Epidote 
when the rocks containing them have been subjected to the factors which 
have produced contact-metamorphism. In a few cases Biotite, Horn- 
blende, and some other minerals, have been produced in the same 
way. In the case of Agates, which have been formed in the vapour- 
cavities of the eruptive rocks by the agency of underground waters, the 
Chalcedony has passed into the crystalline condition, and has now become 
Quartz. ‘This is, perhaps, one of the reasons why normal agates are so 
rarely found in Cumberland. 
In some instances of extreme contact-metamorphism of the Cumber- 
land volcanic rocks the determining factors have probably been con- 
nected with the uprise of heated alkaline waters, which have operated 
upon the rocks in question before they have lost their alkalies through 
prolonged exposure to surface agencies. The rocks belonging to this 
category are chiefly confined to the heart of the older volcanic rocks. 
It is possible that some of the anomalies presented by the rocks and 
minerals of Carrock Fell, which have formed the subject of an important 
memoir by Messrs. Harker and Marr, may be explicable in this way. 
Mr. Ward regarded this complex as a case of old lavas altered m situ ; 
and although this view has recently been questioned, there is still much 
to be said in its favour. The present writer is disposed to regard the 
minerals composing the complex in question as due to the influence of 
heated waters containing alkaline matters, which have risen through an 
older set of lavas and tuffs at an early period in their history, and before 
the volcanic rocks had lost any of their essential constituents by weather- 
ing. The granophyric rock associated with these altered lavas, may, on 
this view of its origin, be regarded as one in which an old basic or sub- 
basic mass has been softened, and subsequently recrystallized, mainly 
through the local operation of heated alkaline waters, which have 
imported into the rock a higher percentage of both silica and the alkalies. 
The intimate association of granophyric rocks and gabbros, here and else- 
where, can thus be readily enough explained. The constituent minerals 
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