190 BALDERSTON : GLACIAL ACTION NEAR INGLETON. 



these boulders assume the appearance of a lava-trap ; (8) One small 

 and another very small block, derived from the Red-dyke, consisting 

 of micaceous syenite, but none evident as having come from the 

 dyke or ridge of hornblendic grey-granite; (9) Two boulders of silver- 

 grey trap, specially described to the Yorkshire Boulder Committee ; 

 (10) A few of the limestone examples may be referable to the Coniston 

 Calcareous bed; (11) The stratum of Silurian conglomerate is also 

 sparingly represented in the boulder system. 



The Limestone and Sandstone boulders are usually smoothed 

 and rounded; the hard, non-fissile Silurians are in many cases 

 broken and angular, in others smooth and somewhat polished, and 

 in a few, striated or marked by traces of glacial grooves and scratches. 

 The same remarks regarding angularity and the absence of rounding 

 and scratching apply to the blocks of derivative, green Porphyry — 

 * Silurian grits.' The small blocks of micaceous syenite have both 

 been smoothed, whilst one boulder of silver-grey trap has been 

 distinctly rounded, but appears to some extent to have weathered 

 again rough, so as to have lost some of its smoothness ; on the other 

 hand, another example is decidedly angular, yet has retained a great 

 degree of smoothness. Above the Drift, lying upon it or in the 

 watercourses below its slopes, are the porphyritic boulders of class 

 7, sometimes found in considerable abundance, especially in the 

 last-named situation, or along the edges of the old glacier-line of the 

 Doe, even up to an altitude of 800 feet on the S.E. boundary, or 

 550 feet on the N.W., where the Twistleton promontory reaches its 

 highest level, and where the line of junction of the glaciers of the 

 Doe and Twiss must have been. As the glaciers receded, the 

 boulders falHng from the edges of that in the Doe valley were left 

 on ground at a lower level, but not so in the Twiss. Why not? 

 Because none of these boulders descended the Twiss valley, the 

 porphyritic patches, if any, not being exposed in this dale, the 

 prolongation of the strata in which those of the Doe occur, lying 

 below the limestone of Kingsdale even now, for a time at least, safe 

 from erosion and denudation. How is it then, that in the lower 

 part of the Twiss ravine the same blocks and boulders are found ? 

 The answer appears to be that the glacier of the Doe being the 

 longer and stronger of the two, overlapped its partner, or drove 

 it to some extent to the west, and so let fall some of its freight in 

 this region. Good examples of the green porphyritic erratics may be 

 seen opposite the mouth of the Catleap stream, but a few yards further 

 down the Doe, a little to the N.W. of the road on Storrs Comm.on, 

 at a point near the Bull-copy, and in Fell-end pasture, above the 

 same Common. 



Naturalist, 



