20 J. CLTPTON WARD ON THE GRANITIC, GRANITOID, AND 



groups, separated from one another by uncertain lines. We shall 

 now see that the microscopic examination, made after the field- 

 work was completed, fully confirms this. 



4 a. Spherulitic Felsite (Carrock Pell, Eae Crags, Great Lingy 

 Hill). — Specimens taken from various parts, along the line of strike 

 of this rock, all show the same general microscopic structure, which 

 is as follows *. 



In plain light the base has a felsitic appearance but with indica- 

 tions of a radiate structure from numerous points, while scattered 

 abundantly over this generally pale and hazy base are long greenish 

 and dichroic fibres, and irregular patches and streaks of a green and 

 greenish-brown mineral, which is apparently converted in many 

 parts into a dark brown or black product. Occasionally a lew 

 small grains of quartz may be distinguished apart from the felsitic 

 base, and crystals of felspar occur porphyritically imbedded. 



In polarized light, between crossed Mcols, the radiate spherulitic 

 structure of the base comes out admirably, a dark cross rotating 

 with the turning of either prism. The spherulites have invariably 

 a radiated and no concentric structure ; and their margins are very 

 seldom definite, but interfere with each other or become blended 

 with the general felsitic base (fig. 6, PL II.). Their average size is 

 about ^j of an inch in diameter. Under crossed Mcols a good 

 many particles of free quartz may be detected in the base, which 

 exhibits the usual felsitic reaction on rotating either prism. The 

 felspar crystals seem to be mostly orthoclase in some specimens, 

 while plagioclase abounds in others. The green fibres appear 

 to be hornblende ; but very little of the greenish mineral seems to be 

 in an unaltered state. 



The rock, or parts of the rock, on Great Lingy Hill, are less 

 spherulitic and more crystalline than that of Carrock summit ; pla- 

 gioclase crystals are numerous, and free quartz abounds, while a 

 highly reticulated felsitic structure appears between the crystalline 

 portions, apparently the remains of the spherulites. 



A specimen from Rae Crags is intermediate between this last and 

 the Carrock-summit rock. It is more crystalline than the latter, 

 and more distinctly spherulitic than the former. 



The example of contemporaneous trap-like rock mentioned as 

 occurring on Pike, Carrock Fell, has the following microscopic 

 structure. In ordinary light, numerous green dichroic fibres and 

 particles appear scattered on a hazy felsitic ground; but with a high 

 power (5 inch) some ghosts of small crystalline needles appear. 

 Between crossed Nicols the base at once assumes a semicrystalline 

 appearance, many small white prisms upon a felsitic ground, with 

 scattered particles of the altered green mineral. I could, however, 

 detect no trace of the development of a spherulitic structure. 

 Altogether I am strongly inclined to think that the microscopic 

 examination tends to confirm the suggestion of its contemporaneous 

 trap-like origin derived from its outward aspect and I therefore 



* Only the general structure of each group will be here described, all details 

 being reserved for Survey publication. 



