2, BIRDS OF CHESHIRE. 
except on its eastern confines is seldom more than 
from two to three hundred, and in some places less 
than one hundred, feet above the sea-level. South- 
ward, however, from a promontory overlooking the 
Mersey near the mouth of the Weaver, runs a tract of 
high ground, which attains an altitude of over 500 feet 
at Harrol Edge, Eddisbury Hill, and Beeston Castle, 
and over 700 feet in the neighbourhood of Peckforton 
and Bickerton. In the east the sandstone rocks of 
Alderley Edge, rising abruptly from the surrounding 
level, reach at their summit the height of 604 feet. 
The northern portion of the Plain is drained by 
the Mersey, whose polluted waters are merged in the 
Manchester Ship Canal near Carrington. Within the 
memory of persons still living, salmon ascended the 
Mersey every year to spawn in its upper reaches; but 
now, running as it does for the greater part between 
artificial banks and gathering fresh impurities with 
every mile, it is doubtful whether the river contains 
any fish below Stockport, and it offers few attractions 
for birds. Gulls of various species, however, work their 
way up the stream from the tidal waters, and it is 
noteworthy that these visitors have increased in 
numbers since the Ship Canal was opened, whilst a 
few pairs of Common Sandpipers still feed their young 
on the banks of pebbles formed by the swift current, 
and Sand Martins tunnel their nesting-holes in the 
soft banks. Near Heatley the Mersey receives the 
tributary waters of the Bollin, which rises in the Hill 
Country and is early contaminated by the refuse of the 
Macclesfield factories. From that town to its conflu- 
ence with the Mersey, it flows through an agricultural 
district, where it is augmented by the streams of the 
Dean and Birkin, finally reaching the Mersey in a 
