582 



J. CLIFTON WAED ON THE GEANITIC, GEANITOID, AND 



regard the mass of Shap Granite as representing an unsuccessful 

 effort towards the formation of a volcanic centre. Had we, indeed, 

 evidence amongst the higher strata of the Upper Silurian or in the 

 Old Eed period of volcanic outbursts in this district, and were the 

 nature of these volcanic products such as are likely to have proceeded 

 from the Shap Granite as the base of a volcanic centre, we should 

 have good reason to affirm that in the Eskdale Granite, the Shap 

 Granite, and the trachytic or felsitic lavas we saw an epitome of 

 volcanic action — the deeply-seated origin, the very bottom of a 

 volcanic neck, and the lavas poured out at the surface. It is 

 possible that such volcanic outbursts did take place in the earlier 

 part of the Old Eed period; but if so, the enormous amount of 

 denudation (to which reference has already been made) which took 

 place during Old Eed times, must have completely destroyed all 

 traces of the volcanic products. 



This view of the relation which the Shap Granite bears to the 

 Eskdale is rather strengthened by the fact that the metamorphism 

 around the area of the latter is much more intense and widely spread 

 than around that of the former. If any force be allowed to the 

 above considerations, it becomes all the more clear that these granites 

 can bear no direct relation, as sources, to the great series of Lower 

 Silurian volcanic beds in the midst of which they occur, but that 

 they are more recent in date. 



The relations of the Eskdale and Shap Granites may be thus put 

 in a tabular form : — 



5. Eskdale. 



^=•166. Ifp=0, the min. temp. 

 =244° C. (471° F.). 



Top of Upper Silurian. 

 V 22,000. 



II 

 fi 



P IP 



tlfl 



Sorby's estimated Fox's calculated 

 temperature of temperature at 

 solidification oi this depth, 259° 0. 

 granites, 360° C. (499° F.). 

 (680° F.). 



*/.-=-166 

 .\ calculated pressure (p>) = 42,000. 



This gives : — 

 Downward press 



! 



22,000. 



nrplus pressure 



1 



20 000. 



3^ 



6. Shap. 



150. Ifp=0, the min. temp. 

 .'-228° C. (442° F.). 



Top of Upper Silurian. 



Hi i 



V 14,000. 



Fox's calculated 

 temperature at 

 this depth, 168° O. 



(335° F.). 



Sorby's estimated 

 temperature of 

 solidification of 

 granites, 360° C. 

 (680° F.). 



0=-15O 

 .'. calculated pressure (p) = 46,000. 



This gives : — 



Downward pressure Surplus pressure 



32,000. 



14,000. 



