SPRINGS. 265 



freezes ; and though its course is little more than a mile before it arrives at the sea, yet 

 eleven mills are put in motion by it. The spring issues from the rock into a beautiful 

 polygonal well, over which the Stanley family erected a chapel about the time of 

 Henry VII. Upon the windows the chief events of St. Winifred's life are painted. The 

 saint is reported to have been a virgin martyr who suffered upon this spot, the spring 

 miraculously rising from her blood ; and hence the veneration for the well in popish 

 times. Pennant says of his own time : " The custom of visiting this well in pilgrimage, 

 and offering up devotions there, is not yet entirely set aside. In the summer a few are 

 still to be seen in the water, in deep devotion, up to their chins for hours, sending up 

 their prayers, or performing a number of evolutions round the polygonal well. In the 

 year 1686 James II. visited this well, and received as a reward a present of the very 

 shift in which his great grandmother, Mary Queen of Scots, lost her head." There are 

 springs similarly powerful along the confines of the limestone district, which vary very 

 little in their quantity of water, either in drought, or after the heaviest rains. About 

 Denton, in Yorkshire, the roaring of the waters is incessant. 



2. Intermittent. Many springs gush with vehemence, then subside, shrink away, and 

 disappear, renewing their tide in its full strength at irregular intervals. They clearly 

 derive their supply from the last rains, and hence fail altogether in dry seasons. On the 

 chalk downs of the south of England, in Wilts and Dorset, it is a very common circum- 

 stance for the valleys to be quite dry in one part of the year, and very fully watered in 

 another ; and hence a Wiltshire proverb says, 



" As the days lengthen, the springs strengthen." 



But we may suppose such a cavity in a hill as A in the diagram, a reservoir fed by rain 

 percolating through the superior rocks, and communicating with the surface by an arched 

 channel, like BCD. As long as the water in the cavity is above the level of the channel 



at c, it will escape through it, and gush 

 out at D ; but the spring will cease when 

 the water of the interior basin has been 

 reduced to that level, and not be re- 

 newed until it rises above it. The flow 

 of the spring will also be more impetuous 

 in proportion as the water of the cavity 

 accumulates above the vertex of the 

 siphon-formed arch. This is the prin- 

 ciple of the Artesian wells, which have 

 been constructed with signal success 

 near many large cities occupying level 

 sites, and formerly inconvenienced by 

 the want of natural springs, or by the 

 bad quality of the surface water. The action of these wells, puits Artesiens so named 

 from the province of Artois, where they have been long in use is due to the constant 

 endeavour of liquids to find their level. If we suppose a basin-shaped country, or a 

 plain enclosed with heights, the rain which falls on the circumjacent hills being absorbed 

 among the rocks, may be conducted through one of the underlying strata of the plain, 

 completely occupying it, and yet be prevented from sinking lower, and also from reach- 

 ing the surface, by inferior and superincumbent beds of solid rock or impervious clay. 

 In such circumstances a perpendicular perforation or boring into the ground is made, 

 penetrating the superior impervious bed, and reaching the saturated stratum through 

 which the water rises to the surface. Thus suppose a town situated upon a bed of clay 



