20 



THE STRATA OF HALIFAX. 



The strata of our neiglibourliood consist of Mill-stone Grit and 

 Coal-measures. If we take our stand on liingby-hill, or even on the 

 roadside just under Ringby, we shall have a very good view of the 

 country aroimd Halifax. We shall see that the land slopes down from 

 the heathy moorlands of Ogden and Warley, towards Ovenden and 

 Halifax ; and, if we neglect the deep valleys of Wheatley and the Calder, 

 we shall see also that the whole country right across to the Ainleys and 

 down to EUand is one plain gradually sloping to the south-east. The 

 whole of this plain is capped with a thick deposit of sandstone rock. 

 Along the edges of the above valleys numerous quarries are opened into 

 it, and in some jjarts excellent building stone is obtained. The new 

 Railway to Ovenden is being cut through it and very good sections may 

 be seen at the town (under Mount Pleasant) and at Skircoat quarries. In 

 fact wherever excavations are made in this plain, this gi'itty sandstone is 

 met with. This sandstone rock forms the uppermost member of the 

 Millstone Grit series and it is fi-om 54 to 70 feet in thickness. The lowest 

 bed of this rock may be seen reposing on a great thickness of shale, at 

 Shroggs Wood, on the roadside leading to Wlieatley. Below this grit-rock 

 there is a great thickness of blue and purple shales highly impregnated in 

 sonie places with oxide of iron, and interstratified with beds of grit-rocks 

 and thin layers of impm-e limestone. The deep valleys of the Calder and 

 its tributaries from Salterhebble to Hebden Bridge, and the Wheatley 

 valley from Dean Clough to Brookhouse and the moorlands of Ogden, 

 Fly, Oxenhope, &c., are composed of this very perishable shale. Atmo- 

 spheric causes, such as rain, fi-ost, Avind, the carbonic acid of the air, &c., 

 have doubtless done a great deal towards forming these valleys, for they 

 act with great force upon these yielding shales, undermining the hard 

 grit-rocks above, until they give way and fall into the valley below, where 

 in course of time they become broken up and carried away by the waters. 

 This breaking up of the grit-rocks is facilitated by the natural fissures by 

 which all hard rocks are divided into blocks. When the shales underneath 



