NOETH-WEST llEGION OF CHAKNWOOD FOUEST. 



80 



in many of the volcanic breccias of Charnwood Forest-, is cer- 

 tain. The structure might be explained by flo\Y-brccciation, but 

 there is nothing to suggest this, and the absence of any fluidal 

 structure in the matrix is opposed to this hypothesis. Though 

 indications of some mechanical disturbance can be perceived almost 

 everywhere, and brecciation may be occasionally due to it, those 

 usually significant of the crushing in situ of a large mass of rock 

 arc certainly not common. The " shaly bands," of course, prove 

 mechanical action ; but our examination of the less crushed portion 

 (on the southern side of the pit) convinced us that the breccia had 

 practically arrived at its present condition prior to the crushing. 

 This appeared to be due to the same cause as that which produced 

 the rough cleavage more or less perceptible throughout the mass. 



On the whole, after examining several carefully selected si^ecimens, 

 we still incline to the view of a pyroclastic origin for the main mass 

 of Bardon Hill, while we would not exclude the possibility of 

 some portions being small flows of true lava. The fact is, as we 

 stated long ago, that the micro-mineralogical changes — the devitri- 

 fication, and subsequent decomposition, the formation of viridite, 

 epidote, &c. — have so " blurred " the structures as to leave us alwayS' 

 in a state of uncertainty as to the right interpretation *. 



We are not aware that any analysis of the Eardon rock has been 

 published ; therefore the following, kindly made for us by Mr. Lord in 

 the laboratory of University College (London), may be interesting. 

 The specimen selected represents the compact green rock, without 

 brecciation, which, as mentioned above, has the closest resemblance 

 to a felstone. Evidently, like the rocks of the Peldar-Sharpley region, 

 it is rather intermediate in character, and nearer in composition to 

 an andesite than to a sanidine-trachyte. It is rather more acid than 

 the Markfield " syenite," and less so than that from Croft Hill. 





SiO, 



A1,0, 



! • 

 Fe,0,| JFeO ! CaO 



1 1 



MgO 



K,0 



Na,0 



Total. 



No. L... 

 No. II.... 



59-86 

 59-00 



16-00 

 16-00 



4-47 

 4-50 



3-64 

 3-70 



8-06 

 8-00 



3-90 

 4-20 



1-20 

 1-36 



2-60 



1-84 



99-73 



98-60 



1 



Loss by drying and ignition not estimated. 



There have been shown to us some small portions of copper-ore 

 found in quarrying, which contained apparently, with malachite 

 and cuprite, a little native copper. A vein of jasper has also been 

 met with. 



* The structures frequentlj^ present considerable resemblance to those of the 

 Peldar-Sharpley porphyroid, but the rock seems to be less quartzose ; beyond this 

 there is nothing that calls for very speciid notice. The rock of Eirchwood Plan- 

 tation, a greenish felstone-like rock (noticed in vol. xx.xiv, p. 206), presents 

 difficulties similar to those ofthe more compact variety of the rock in Bardon 

 Pic. In one place it is very like a felstone ; in another a structure appears 

 faintly outlined which does not resemble a result of crushing, and suggests a 

 pyroclastic origin. 



