THE MEASUREMENT OF BAIN. 



15 



slightly above the surrounding table land, the elevation of 

 which, from the crests of the valleys just described, varies 

 from 1500 to 1900 feet. — The millstone grit caps the sum- 

 mits in various parts, forming occasionally perpendicular 

 precipices several hundred feet in height; and in other parts 

 the sides of the valleys consist of beds of indurated shale. 

 Some considerable portions of the tops of the hills are 

 covered with peat and others with gravelly clay. The more 

 easterly portion of the district consists of the lower coal 

 measures. 



For hills of this elevation it is scarcely possible to find 

 any which, from their position and character, would be more 

 likely to induce a large fall of rain, or to allow a larger pro- 

 portion of that which falls to flow down the streams. It is 

 from this district that the town of Manchester is to be 

 supplied with water. 



Measurements of the volume of all the various streams 

 have been made daily since the end of 1846, and rain gauges 

 have been placed at various elevations and at different 

 parts of the district, from which the quantity of rain which 

 has fallen has been ascertained. 



In an adjoining valley, down which flows the Swineshaw 

 Brook, a tributary of the river Tame, similar observations 

 have been made since the end of 1844. This valley lies 

 nearly east and west, and is completely land-locked, turn- 

 ing abruptly to the north through a narrow glen just before 

 it joins the river Tame. The summit of the valley is at 

 Windyate Edge, which is the summit also of two tributaries 

 of the Elherow, the Hollingworth and Amfield brooks. 



Rain gauges were placed at the bottom of the Swineshaw 

 valley, near the point at which the volume of the stream 

 was measured, and on Windyate Edge near the summit. 

 For some time also a gauge was kept about midway. 



The brook was measured regularly twice a day. During 

 the years 1846 and 1847, the index rod of the rain gauges 



