314 W. M, Hutchings — A Contact-Rock from iShap. 



Amphibole (Hornblende). 



Observed forms (110), (010), (100), (001), (111). The faces are 

 very small (0"2 mm.) and feebly reflecting; the observed average 

 inclinations diifer by about half a degree from the calculated 

 inclinations. The crystals have a black colour, resinous lustre, and 

 are opaque. 



Pyroxene (Augite). 



Observed forms (110), (010), (100), (111).^ 



Average of observed angles. Number of observations. Calculated angles, 

 no A 010 43° 10' 3 43° 35' 



110 A 100 46° 45' 3 46° 25' 



111 A 010 60° 0' 1 60° 24' 



The crystals elongated in the axis C are extremely small, but 

 have brilliant faces, vary in colour from greenish to brownish- 

 yellov^f, vitreous lustre, are translucent, and exhibit marked chromatic 

 polarization. On the bigger crystals are implanted obliquely smaller 

 ones, in both of vsrhich w^hen digested in H 01. no alteration could be 

 observed, except slight discolouration. 



Mica o'ccurs in hexagonal laminae, very small in size, and very thin. 

 Very rarely with a strong lens can the faces of the zone (001) be 

 distinguished. The colour is brownish, more or less dull, the lustre 

 between adamantine and pearly, and the laminae are translucent. 

 In some cases the mica is altered, opaque, and has a submetallic 

 lustre. Under the microscope the more coloured laminae show 

 distinct dichroism, and are distinctly biaxial, normal to the base ; 

 but on account of their extreme thinness they do not give in 

 convergent polarized light very distinct curves. In a large pro- 

 portion of the crystals phenomena of reabsorption with the production 

 of ferrite have taken place, and some are completely transformed into 

 a mass of this mineral. 



VIII. — Note on a Contact-Rock fkom Shap. 

 By W. Maynaud Hutchings, F.G.S. 



ONE of the contact-rocks from Shap, which I collected a few 

 years ago, has always presented some points of special interest ; 

 and in view of a recent careful re-examination of it, microscopical 

 and chemical, I think a few remarks upon it may not be out of place. 



It occurs on the slope of Wasdale Pike, high up above the farm- 

 house of Wasdale Head, and appears to be, in the main, the same as 

 the rocks which are described by Barker and Marr in their paper 

 on the district (Quart. Journ. Geol. Soc, vol. xlvii, 1891), and of 

 which they say (p. 308) that they " have a very distinct lamination, 

 and give in the field a suggestion of crystalline schists, or even of 

 gneisses." This description applies fully to the specimens collected 

 by me from a point about 15 feet from the actual contact. 



I first examined the rock a year before I had the pleasure and 

 advantage of going over the ground with Mr. Marr, when I had no 



1 The formula of the faces are those of Miller, and the calculated angles are those 

 in Dana's Mineralogy. 



