I40 BALDERSTON : THE SILURIAN ROCKS OF INGLETON. 



green, a little ; hornblende, green ; mica, black, pale green, and 

 silvery ; idocrase, some ; schorl pseudomorphs, a few ; quartz, 

 seldom observed. The extreme points of exposure are 748 yds. 

 apart. 



No. 6. — The Lane Dyke. One exposure only, and this in and 

 close to Tvvistleton Lane, and on the exact prolongation to N.W. of 

 No. 5, but is evidently a branch of No. 4; it much resembles the 

 Upper Dyke at Coombe near Dent; width, 21 in.; altered and 

 weathering quickly ; bluish white, weathering yellow. Constituents : 

 pale grey felspar ; hornblende, almost indistinguishable ; mica, 

 black and pale, small ; quartz, occasional clusters ; a few stains, 

 suspiciously like those of No. 4 ; texture very compact. Exposure 

 not more than 10 yds. 



No. 7. — The Quarry Felstone Dyke, (i) At Pecca Slate Quarry, 

 here about a foot thick, (ii) In the Slate Quarry, N.W. of the Doe, 

 and here 2 ft. thick ; other exposures undoubtedly in the same series 

 of slates, besides minor and thinner bands, which are, no doubt, 

 branches from the main outburst; 331 ft. of slate and ash between 

 position (ii) and dyke No. 5. The condition of the trap is moderately 

 fresh, but the compactness varies ; the line of exposure seems to vary 

 little, but in the Doe quarry has evidently crossed to a point a little 

 nearer the N. Eastern edge of the slates. Constituents : composed 

 of a slightly granular to compact mixture of quartz ; pale to warm 

 tinted ; felspar ; small scales of mica ; and a little hornblende. 

 Extreme points of exposure named, 968 yds. 



No. 8. — The Great Black Dyke; has twenty-one or more exposures; 

 near the Skirwith Road, or to the S.E., 555 ft. of Galliards and a little 

 slate intervene between it and the line of No. 7 ; in Doe Gill 

 the amount is about 630 ft. ; and in the Twiss 770 ft., where it has 

 actually run into Group 5 of the stratified series, which is a great 

 Green Slate series, (i) At Thornton Foss, just below the pool, two 

 exposures, about 3 ft. wide, and much decomposed; the dyke runs from 

 this point under Silurian conglomerate to the S.E., for a considerable 

 distance covered by Scar Limestone, etc. (ii) In the Twistleton 

 fields and lane again comes to the surface, just within the N. Eastern 

 edge of the Galliard series, Group 6, where it yields eight exposures 

 or more, varying from 5 ft. to 10 ft. in width, which, for the most 

 part, are much decomposed, (iii) In the Doe, one long and sharply- 

 flexed exposure, if ft. wide, in good condition, but having much 

 porphyritic calcspar, and the adjacent beds greatly altered for a con- 

 siderable distance. In the gully on the opposite side of the stream, 

 but lower down the river, is a chloritic extinction -dyke that may 

 belong to this dyke or to No. 9, which both, where last seen near this 



Naturalist, 



