xiv. THE FLORA OF HALIFAX. 



S ii is rich in organic matter, the peat retains a large amount 

 of moisture. The prat flora is exceedingly weak in number of 

 species, though the e present in countless myriads. 



me further surface features of the parish remain to be 

 noticed, especially these that have been influenced and deter- 

 mined by man. The plateau is deeply cut 

 Form of both by the central and lateral valleys. The 



Valleys. hills lack ruggedness of outline and contour. 



'I' hey form gentle shelving slopes, often des- 

 cending in terraces, 'caused by the alternation of sandstone and 

 shale. The streams, at first, only make a gentle depression in 

 the contour : so long as they remain on the moors the valleys 

 are not cut deep, though the gradient may be considerable ; 

 but when the stream has descended to about 1,000 or 8ooft., the 

 valley alters in character and becomes what is called a clough, 

 or, less frequently, a dean. The stream is here cutting down 

 through the strata, which hem it in on both sides, so that it 

 has the appearance of having cleft the rocks. This portion of 

 the valley is generally densely wooded, the woods clothing the 

 steep sides, but stopping short above where they take a more 

 gentle slope, occupied by pastures and farms up to the moor 

 edge. From 500 feet downwards the gradient becomes less and 

 the valley broadens out somewhat, and admits of a hamlet or 

 village, though it hardly loses its clough-like character, as the 

 moors follow it in parallel lines to the main valley. There is 

 no case of a tributary entering the Calder above its level and 

 so forming a cascade, nor are there any noticeable waterfalls 

 except at Walshaw, and Lumb Fall in Crimsworth Dean, 

 where the stream first meets the Yoredale rocks. Though the 

 western doughs have been mainly considered so far, the 

 general features of Cragg Vale, Ryburn valley, Blackburn 

 valley, Luckkiulen Dean and the Hebble valley are similar. 

 But tin- valley of the Red Beck flowing through Shibden to 

 Brookfoot, and of Clifton Beck, both on the Coal Measures, 

 are not so steep and narrow, on account of the more rapid 

 weathering of the softer rocks out of which they are carved. 

 There is no natural sheet of water in the parish, and hardly 

 a pond, so that beyond the streams and moorland bogs, the 



botanist is dependent upon artificial habitats 

 Canals. for the occurrence of aquatic plants. Of these 



there are three : reservoirs, mill-dams and the 

 canal. The reservoirs are numerous, but being kept clear of 

 vegetation, they are of no importance botanically, except in so 



