124 



(Quartz crystals, as is well known, occur along with the Hematite, 

 perhaps as one result of the complex series of chemical changes 

 initiated by the infiltration of the solutions that brought down 

 the Gypsum, the Rock Salt, and the Carbonate of Magnesia into 

 the Red Rocks. Crystals of quartz occur now and then lining the 

 interior of Carboniferous fossils, but such instances are far from 

 common. 



Quartz is not the only form of Silica that occurs in Edenside. 

 Chalcedony, which is regarded as a mixture of the crystalline 

 form of quartz with the opaline form, is found here and there, 

 generally in association with nodules of chert, in various parts of 

 the Carboniferous Limestone series, notably in the part of the 

 Mountain Limestone about the upper part of the Luna Valley 

 between Tebay and Ravenstonedale. 



The Chert just mentioned is another form of crypto-crystalline 

 silica, which differs from flint in having a more splintery fracture, 

 and in including, in its impure forms, much Calcic Carbonate in its 

 composition. Chert occurs in interrupted nodules in the Mountain 

 Limestone of the part of the Lune Valley just mentioned ; and 

 some of these nodules are clearly the result of segregation around 

 a fossil nucleus ; generally one of the corals, already partly silicious 

 to begin with. Nodules of chert occur also in particular beds of 

 the Yoredale Limestones all through Edenside, as far, at least, as 

 Hesket-Newmarket, on the south-west side, and as Renwick, on 

 the north-east. 



Jasper is another form of crypto-crystalline silica occurring in 

 Edenside ; but its mode of occurrence is different from that of any 

 of the other forms we have been considering. Jasper occurs 

 principally as one of the constituents of the pebbles that go to 

 make up our Upper Old Red Conglomerates — that group of 

 conglomerates and sandstones whereof patches are left here and 

 there between the Carboniferous Rocks and the Older Palaeozoic 

 Rocks of the Lake District. This Jasper is found in deposits of 

 the same age and character on the flanks of the Cheviots ; and as 

 many of the rock fragments occurring in our deposits of the Upper 



