151 
other prominent points than those already noticed, must be 
shown by a diagram of the system of drainage, correctly 
drawn for me by Mr. D. Kershaw, by which gentlemen from 
a distance will better understand the districts referred to 
than by local names, the course of the Calder being more 
generally known. 
To the Westward of the township of Wyke, in Birstal, 
which forms the boundary of this parish on the east, the 
alternating clay, shales, coal, and sandstone suffer condensa- 
tion, as may be partially seen in the excavation on the Brad- 
ford road, until they arrive at Halifax, when they, together 
with the rest of the upper grit group to which they belong, 
become extinct for some miles distance in the same direction, 
A belt of plate coal, however, is discernible from the railway 
line, situated within the middle millstone group in Norland, 
as also in Sowerby ; and still further to the North a thicker 
seam is found in Midgley, but its extraction is rendered 
difficult, if not impracticable, from its dip and drainage ; 
whilst still to the West beyond Hebden Bridge, and to the 
North of Heptonstall, the Millstone grit is more fully devel- 
oped, overlying the Yoredale series. For reasons already 
assigned, any computation of the thickness of this formation, 
and its alternating grits, plate, and shales, would prove appli- 
cable only to a given point, their variable occurrence being 
unfavourable to any general accurate admeasurement. The 
upper Millstone grit itself usually occupies the highest 
ground, where its pebbly indestructible nature, affording 
little or no soil, together with the low temperature and humi- 
dity of the air, promotes the growth of heather, sedgy grass, 
mosses, lichens, and other cryptogamic plants ; and in these 
localities it may measure from 70 to 150 feet, or more at 
Studley Pike and Bouldsworth. 
The western part of this neighbourhood may be said to 
resemble in some degree the district from the Wharfe north- 
