310 MESSRS. A. HARKKR AND J. E. MARR ON 



to those in the volcanic breccias and perhaps of direct volcanic 

 origin ; but there are also fragments of decomposing andesite with 

 vesicles filled with calcite, and rolled crj-stals of striated felspar 

 [862], Some of the lower beds exposed in the Upper Coniston 

 Limestone division are more gritty in appearance, and one contains 

 plenty of rounded quartz and fragments of spherulitic i-hyolite, as 

 w^ell as ashy material [1077]. This bed is interposed between two 

 flaky agglomeratic ashes, and the admixture of volcanic material 

 with the detrital and calcareous is very clear. The Lower Coniston 

 Limestone here offers no characters which call for notice. 



Although the limestones in our district cannot be followed in 

 continuous exposures from the unaltered to the highly altered state, 

 we can obtain a general idea of the extent and progress of the 

 metamorphism by comparing specimens from different spots. As 

 already stated, theBlea Beck rocks are in general unaffected by any 

 thermal metamorphism, but one or two specimens show the begin- 

 ning of the change in the development of a few scraps of a pyrox- 

 enic mineral, evidently formed at the expense of part of the calca- 

 reous material. This is at 1400 yards from the granite [870] ; 

 (compare with [1077] from the same locality, which is quite un- 

 altered). A specimen taken west of the small plantation near 

 Wasdale Beck, about 1000 yards from the granite, shows more of 

 the lime-silicate with less calcite [906]. This rock, like the pre- 

 ceding, is a calcareous ash, though it belongs to a lower horizon. 

 We shall notice in its proper place a calcareous rock in the Silu- 

 rians, which is well seen at Backhouse Hill, about 600 yards from 

 the granite. There lime-silicates are abundantly present, and only 

 a rare patch of the original calcite is to be seen [1225]. Finally, 

 in the exposures of Coniston Limestone near Wasdale Head Farm, 

 at distances of 300 yards and less from the contact, all trace of the 

 original calcareous ingredient is merged in metamorphic products. 

 The progressive modification thus indicated is more gradual than 

 that recorded in Lossen's metamorphosed limestones around the 

 granite of the Bamberg. 



In the Wasdale Head section, as already stated, both Upper and 

 Lower Limestones occur in a highly altered condition, the carbonic 

 acid having been completely expelled with the production of various 

 crystalline silicates, which are, naturallj', minerals rich in lime. 

 The Lower Limestone may be found, with some difficulty, in two 

 small '• sikes " west of the farm, and was discovered here by Profs. 

 Harkness and Nicholson, who recognized it as a metamorphosed 

 limestone containing idocrase. The Upper Limestone, though much 

 better exposed, and close to the farm-road, seems to have escaped 

 notice. It is to be observed that the uppermost and purest beds 

 are not seen in this section, which shows only part of the Calcareous 

 Breccia and a few feet of the overlying strata. The small part of the 

 Lower Limestone that is accessible also seems not to belong to the 

 most purely calcareous portion ; and, indeed, in both limestones the 

 presence of various aluminous silicates points to some original ad- 

 mixture of earthy or ashy material, as well as the possible intro- 



