480 
ON THE SO-CALLED INGLETON GRANTTE. BY THOMAS TATE, F.G.S. 
Under this commercial name a rock has recently been brought 
into the market for road metal. It is quarried in the Borrowdale 
Series underlying the Mountain Limestone forming Twistleton Scars 
on the north-west, near to Dale Barn, and Raven Scars on the south- 
east ; extending thus quite across the Dale above Ingleton, having a 
thickness of about 400 yards, with a sharp dip to the south-west. 
This rock has given rise to much discussion locally, as to its 
origin. It has been variously described in published records as a 
conglomerate, a trap, a felspathic ash, and as a metamorphic slate. 
As to the texture of the rock, no one of its components is con- 
spicuously larger than the average of its fellows ; each layer exhibits 
a uniform grain, but the layers graduate from about one-eight of an 
inch down to the finest granules. This marked uniformity along 
successive planes points to the sorting action of gravity exerted upon 
materials held in aqueous suspension. Sedimentation is further in 
evidence by the parallelism of all the longer axes and the stratifica- 
tion arising therefrom. Beneath the microscope most of the ingredients 
are seen to be sharply angular, nevertheless a fair proportion are well- 
rounded and water-worn. 
The detritus of a quartzite has supplied many of the clastic 
elements. Next to this come crystals of quartz and felspars, both 
orthoclase and plagioclase, the latter being the more abundant, 
relatively, in the finer-grained layers. Ancient lavas, both acidic 
and basic, devitrified spliierulitic rhyolites, augite, andesites, and 
deep-seated micropegmatite have contributed of their spoils. 
These detrital products, enclosed in a volcanic ash matrix of a 
diabasic character, have consolidated into a tough rock of low-specific 
gravity (2"693), and possessing great tenacity. 
With the exception of a few strain-shadows along the margins 
of quartz grains, the micro-slides offer no suggestions of the ingre- 
dients having suffered from mechanical deformation. In the quarry, 
however, may be noticed one or two quite local examples of schis- 
tosity resulting from shearing, in close proximity to shrinkage joints, 
now infilled with quartz and a green earthy degradation product. 
