598 



J. CLTFION WARD ON THE GRANITIC, GRANITOID, AND 



however, the analysis of the specimen taken from a point nearest to 

 the granite, is contrasted with these, a more marked difference is seen, 

 the amount of silica being 14 per cent, less than that in the gra- 

 nite, and that of alumina, lime, and ferrous oxide considerably more. 

 It will be at once acknowledged that so few analyses of so large 

 an area of rocks can but give a very general idea of the true average 

 composition ; and it would be very unwise to affirm that No. 3 neces- 

 sarily represents the average composition of the altered rocks close 

 to the granite. It has, indeed, been already pointed out that the 

 microscopical structure of this specimen shows it to be more than 

 once removed from the typical granite ; and an analysis of the rock 

 whose microscopic structure is represented in fig. 5 might give a 

 somewhat different result. It may well be, in fact, that the speci- 

 men chosen for analysis from near the granite, in this instance, was 

 from a rock differing originally in a more or less marked degree 

 from the neighbouring masses, as considerable differences are known 

 to prevail amongst these volcanic rocks as a group ; and indeed, if 

 we compare No. 3 analysis with analyses of the contemporaneous 

 traps of the district *, we find them strikingly similar, thus : — 





Contempora- 

 neous Trap. 

 Brown Knotts 

 near Keswick. 



Contempora- 

 neous Trap. 

 Iron Crag- 

 near Keswick. 



Altered Con- 

 temporaneous 



Trap ? 



LingmellBeck, 



Wastdale. 



Silica , 



60-718 



14-894 



6-048 



1-909 



2354 



2-843 



6-426 



1-405 



•395 



•281 



•103 



1-660 



•964 



59-511 



17-460 



5-376 



1-801 



3-705 



3-093 



4-926 



1-271 



•604 



•115 



•086 



1-569 



•483 



59-151 

 19-212 



5-208 



1-909 



2-933 



4-217 



5-192 



•879 



•360 



•439 



trace 



trace 



•500 



Alumina 



Lime 



Magnesia 



Potash 



Soda 



Ferrous oxide 



Ferric oxide 



Bisulphide of iron 



Phosphoric acid 



Sulphuric acid 



Carbonic acid 



Loss on ignition 





100-000 



100-000 



100-000 



So that it seems probable that the analysis No. 3 may be that of 

 a contemporaneous trap. Upon the western side of Lingmell I have 

 traced such traps for a considerable distance, until, unable to follow 

 them further amongst such highly altered rocks, I represented them 

 as dying away upon the mountain- side, one pointing to this very 

 spot, near the granite f. Such a result as the analysis now gives is 

 therefore particularly interesting and satisfactory. 



* Quart. Journ. Geol. Soc. vol. xrxi. p. 388. 

 t See " Lava Bed," on map, p. 592. 



