X. THE FLORA OF HALIFAX. 



this may be, the fact that the valley at Todmorden is only 400 

 feet above the sea level, and at Calder Head only 750 feet, has 

 caused it to become a natural artery for the flow of traffic 

 between south Lancashire and the West Riding, and has 

 largely influenced the history of the parish. This pass differs 

 very much from the only other, but more extensive, break in 

 the Pennine Chain, between Skipton and Settle. The valley 

 of the Calder down to Hebden Bridge is almost a gorge, in 

 places wholly occupied by the railway, road, river and canal, 

 which penetrate through it. Still richly wooded, it must have 

 been at one time, before the river was defiled and the valley 

 blocked by mills, highly picturesque. The more ancient route 

 across this boundary is, however, the famous pass over Black- 

 stone Edge (1277 feet), which maintained its supremacy from 

 Roman times to the advent of railways. 



Eastward from Waystone Edge(i55o feet) the boundary is 

 not quite so natural ; the upper part of Blackburn Valley, 

 known as Dean Head, is excluded, whilst a portion of Fixby 

 Park, which is included in the parish, is in the basin of the 

 Colne. 



The eastern boundary, from Shelf (800 feet) to Brighouse 

 is formed by Royds Hall Beck and Clifton Beck, and for a 

 short distance the Calder, which finally leaves the parish at 

 Rastrick, 170 feet above sea level. 



The northern boundary from Jackson's Ridge to Queens- 

 bury descends gradually from 1500 to 1100 feet, and is almost 

 wholly the true water parting of the Calder and Aire. Perhaps 

 the only exception is on the northern slope of Swill Hill, 

 which is partly included in the parish ; but the area in question 

 is only a few acres. 



To understand the form of the surface of the land 

 within the parish, it is necessary to go deeper and enquire 



what the rocks are, and how they are arranged. 

 Geological From a botanical point of view, the geology of 

 Features. the district is comparatively simple, and a 



short survey will suffice. Further explanation 

 and details will be found in the papers on the Physiograph- 

 ical Features and the Strata of the Parish, by Wm. Simpson, 

 F.G.S., in the first volume of the Halifax Naturalist. 



The upheaval of the Carboniferous system, which produced 

 the Pennine anticlinal, and the subsequent denudation cause 

 all the strata of the parish to dip in a south-easterly direction, 

 and the oldest rocks of the series to appear at the surface in 



