596 J. CLIFTON WARD ON THE GRANITIC, GRANITOID, AND 



the transition is easily made to well- developed granite, being in fact 

 a passage, in this last case, merely from a fine-grained granite to a 

 more coarsely grained one. Fig. 6, representing the microscopic 

 structure, under polarized light, of a fine-grained portion of a speci- 

 men from the edge of the great Eskdale granitic mass, is drawn on 

 the same scale as the preceding figures ; and the difference between 

 this and the last is no greater than would be found to prevail 

 between fig. 6 and a still coarser part of the granite. In this last 

 figure the quartz appears as irregular areas, interfering with one 

 another, "and sometimes containing small crystalline needles as well 

 as included portions of the base and the usual complement of liquid- 

 cavities ; the felspar is both orthoclase and plagioclase, an example 

 of the latter being shown in the centre of the drawing ; and the 

 mica seen in the area represented is of a lightish brown colour*. The 

 specimen thus figured was near that from which fig. 4 was drawn, 

 the line separating the two being pretty well defined. 



What has been hitherto said in the description of microscopic 

 character will apply equally well to the case of the altered ash-rocks 

 around the Shap granite and to those around the Wastdale and Esk- 

 dale granite, with the exception that, the metamorphism being less 

 widely spread in the former case, there are fewer examples of the 

 streaky felstone-like rocks, and no good examples of the last stage 

 described under the head of bastard granite. Nevertheless there 

 are some very curious cases of quartz-felsites, sometimes with quartz 

 apparently replacing large felspar crystals, such as those that occur 

 usually in the Shap granite. One remarkable instance of this is 

 among highly altered rocks just beneath the Coniston Limestone, at 

 Shap Wells ; and in New Inn Gill, distinct large felspar crystals 

 occur imbedded in the matrix of a quartz -felsite, somewhat micaceous. 



In PL XXXI. fig. 7, is represented, on a scale one half that of the 

 other drawings, an actual junction of the highly altered ash-rock 

 and the granite. In the specimen the line of junction is tolerably 

 well marked ; but under the microscope the change appears much less 

 definite, and seems to be in great measure one of degree. The altered 

 rock, a to b, is virtually a quartz-felsite with numerous little specks 

 of brown mica and having an occasional string of coarser grain, c c, 

 running off from the granite through it. The large crystals of felspar 

 and the larger flakes of mica come on rather suddenly, but are at 

 first imbedded in quite the same sort of felsitic matrix as prevails in 

 the adjoining rock, only that it is coarser-grained; and from this to 

 the fully developed granite there is but a step. In the figure, that 

 half of it representing the granite shows a large crystal of plagioclase 

 felspar, a large area of quartz with enclosed portions of base, and an 

 irregular mica flake of some size. 



III. Chemical Composition. 



1. Rock-analyses. — It now remains to be seen how far the views 

 hitherto advanced as to the gradual passage from altered ash-rocks 



* The large and long fragment near the base of the disk and rather to the 

 right is brown mica. 



