68 REPORT — 1855. 



London, and conveyed thence, for a very moderate outlay, exceeds 40,000,000 

 gallons per day. 



The sands of Delamere Forest in Cheshire yield a large quantity of 

 beautiful water, not exceeding 5° of hardness, issuing along the margin of 

 the closer measures on which they rest. From measurements made in the 

 summer of 1851, the gross produce was 16,000,000 gallons a-day, from a 

 tract of country not exceeding thirty-six square miles in extent. 



The quantity of spring-water must of course depend much upon the 

 amount of rain which falls upon the surface, even when the other conditions 

 of the case are similar ; but it is probable that in the two instances last 

 named, there is little difference in the annual rain-fall. The Rev. Gilbert 

 White, in his ' Natural History of Selborne,' gives the average rain at 

 Selborne, close to the Surrey sand district, from thirteen years' observation 

 (from 1780 to 1792), at SS'^S inches per annum ; while at Liverpool, no great 

 distance from Delamere Forest, the average annual rain is about 35 inches. 



Passing from these absorbent measures, which are so eminently productive 

 of springs, to those of older date and harder or closer texture, I am able to 

 give, from extensive observation, some information upon the volume of spring- 

 water produced by the sandstone district of the lower coal-measures and the 

 millstone grit formation immediately beneath. These two groups of rocks 

 usually produce spring-water of great excellence and softness, but owing 

 to their general horizontal stratification, the frequent and great extent to 

 which they are covered by drift clay and the numerous beds of impervious 

 shale with which the sandstones and flag-rocks are interstratified ; and also 

 to the steep and hilly character of the surface which generally prevails where 

 these formations are present, the bulk of the rain which falls runs off the 

 ground in floods, and a comparatively small quantity finds its way through 

 cracks and fissures into the interior of the earth, to be reproduced as springs. 



Hence it is seldom that springs are found here in sufficient volume to 

 supply large masses of population, and a different system of supply has 

 been resorted to, that of storing the surplus water of wet seasons for use 

 in periods of drought, which will form a separate subject of observation. 



The volume of spring-water from equal areas varies considerably in the 

 districts under consideration. 



This is owing partly to elevation, partly to geological differences, but 

 perhaps principally to the very variable quantity of rain which falls upon 

 the surface. Taking the Penine chain of hills, which forms the boundary 

 between the counties of York and Lancaster, and the various projecting 

 spurs of the same range which run into both counties, as the most conspicuous 

 development of these geological formations, the rain is found to vary 100 

 per cent, in the same year, although the district named is confined to very 

 narrow limits. Thus the rain at Liverpool, Lancaster, and Manchester, on 

 the plain beyond the western confines of the district, averages 35 inches per 

 annum ; at the foot of the hills, at Bolton and Rochdale for instance, it 

 reaches nearly 50 inches ; on the hills above Bolton, within the gathering 

 grounds of the district supplying that town, Liverpool, Chorley, Black- 

 burn and other places, the rain amounts to nearly 60 inches per annum. 

 On Blackstone Edge, the summit of the ridge between Rochdale and Hali- 

 fax, and in the Manchester Water- Works district, about half-way between 

 Manchester and Sheffield, the annual rain is upwards of 50 inches. At the 

 foot of the hills to the east, as at Sowerby Bridge and Halifax, it does not 

 much exceed 30 inches ; and further on to the east, as at Leeds and York, 

 it falls to bet ween 20 and 30 inches. 



In like mann er the spring-water varies in extreme drought from about i of 



