84 MR. E. E. WALKER ON THE GARNET-BEARING [Feb. 1 904, 



long plagioclase-crystals (3889), rather turbid and quite unlike the 

 clear labradorite that one is accustomed to see. The extinction- 

 angles correspond rather with an oligoclase-andesine. The ferro- 

 niagnesian mineral is uralite, in greenish fibrous masses which 

 show twinning with (100) as twin-plane, with strings of limonite 

 running along the cleavage. Calcite is developed along the margins 

 of the uralite, and in small patches within the mass. Further 

 change results in the production of an almost colourless and isotropic 

 chlorite. Ilmenite occurs in ragged crystals, with a peripheral 

 growth of brownish sphene. Kods of ilmenite crossing at an angle of 

 60° are also found. In other sections (3892) augite is present as a 

 kernel to the uralite, and the ilmenite has good crystal-outlines. 



At the junction between the basic rock and the banded felsite 

 considerable intermixture has taken place, with the production of 

 an intermediate rock. This intermingling is well shown by the 

 weathered surface of the rock at the junction, which has rather the 

 appearance of a breccia. The intermediate rock is a quartz- 

 diabase (3890). It has the same felspar as 3889, developed in 

 oblong crystals with Carlsbad and pericline-twinning. The ground- 

 mass is of quartz and the same felspar — the two occurring in 

 micropegmatitic intergrowth. 



The banded felsite (3893) shows spherulitic growths of felspar- 

 fibres, either alone or with quartz. Chlorite-flakes representing 

 original mica occur, and these separate off iron in the form of ferric 

 oxide. Muscovite-flakes are diffused throughout the slide. This 

 felsite is undoubtedly connected with a beautifully-spherulitic rock, 

 which occurs just above the wall only a few yards from the Combe 

 Beck. The spherulites have a core of reddish earthy matter, which 

 is seen under the microscope to be the product of the decomposition 

 of the chlorite-flakes that occur either as a central aggregate or in 

 rings. The felsite was probably first intruded, and the diabase 

 came up later. 



To show that intermediate rocks have been produced at the 

 junctiou,I made silica-percentages of these rocks; but unfortunately, 

 owing to a mistake in the numbering of the slides returned to me, 

 I tested only the extreme types : — 



Silica-percentages. Specific gravities. 



Diabase (3889) 50-12 2-830 at 18'3° C. 



Diabase (3892) 49-52 2-831 at 16'8° C. 



Banded felsite (3893) 72-46 2*683 at 20-3° C. 



Banded felsite 72'21 



These diabases resemble very strongly the diabases of Stony Tarn 

 (3880 : see p. 81). It will be seen that, both macroscopically and 

 microscopically, it will prove difficult, if not impossible, to say 

 definitely whether a given dyke belongs to the Eskdale or to the 

 Buttermcre intrusion. From what I have seen of the two rocks, I 

 have come to the conclusion that, if not of the same age, they 

 have been produced from the same rock-magma. Both show rocks 

 of intermediate character containing garnets ; in the case of the 



