125 



Old Red are identical with part of the constituents of their chrono- 

 logical equivalents on the Border, it may be not altogether unsafe 

 to conclude that our Jasper came from some older conglomerate 

 out Scotland way, whose disintegration and subsequent rearrange- 

 ment have given rise to our Upper Old Red Conglomerates here. 

 If this view should hereafter prove to be correct, we need not 

 wonder that the constituents of our Mell Fell and other Upper 

 Old Red deposits do not represent the waste of the rocks of the 

 area adjoining. 



Yet another form of silica occurs in Edenside. This is found 

 in the form of finely laminated siliceous beds associated with the 

 limestones of the Yoredale Rocks. In the south-eastern part of 

 the valley these beds assume considerable importance, and they 

 there occasionally pass into beds of nearly pure chert, notwith- 

 standing their obviously sedimentary and fossiliferous character. 

 These beds graduate horizontally into ordinary limestones in one 

 direction, and in the opposite direction, where we have reason to 

 believe that deep sea conditions obtained during the formation of 

 the Yoredale Rocks — they tend to develop into beds a hundred 

 or more feet in thickness. 



One is tempted to regard these siliceous beds as representing a 

 palaeozoic series of deposits of siliceous mud derived, it may be, 

 from the exuviae of the Diatoms, Radiolarians, and Sponges 

 inhabiting the deep sea at that remote period. Professor Huxley 

 has shewn how deposits of this nature may, by the partial, or the 

 total, dissolution and the subsequent redeposition of their siliceous 

 particles, be converted into amorphous opaline silica. Such 

 deposits as have lately been brought under the notice of the 

 scientific world as one of the results of the Challenger Expedition, 

 would give rise to a set of rocks essentially like those I have just 

 now referred to, if there were frequent oscillations of level bringing 

 about alternate deposits of siliceous mud and calcareous ooze, and 

 these again alternating with ordinary sedimentary and drifted 

 deposits, as the physical conditions changed, 



The quartz crystals occurring in the Penrith Sandstone, represent 

 another and a later period of development. I have before ex- 



