492 D'ggwg of Wells. [Book VII. 



they come to a very hard kind of earth much refem- 

 bling chalk ; here they begin their mafon-work, and 

 build a well, which they carry on at their leifure till 

 they have finished, without being interrupted with one 

 clVop of water> and without any apprehenfion of noc 

 finding it when they come to make the experiment. 

 The well being finished, they bore, through the hard 

 bed of chalk, upon which the well is built, with a long 

 auger, but take care to get out of the well before they 

 draw it out again; which when they have done, the 

 water fprings up into the well, and in a little time 

 rifes to the brim, nay fometimes overflows the neigh- 

 bouring grounds. Now there can be little doubt, that 

 thefe waters flJw from refervoirs which are collected 

 within the Appennine mountains, not far from Modena, 

 and taking their courfe through fubterraneous paf- 

 fages,' endeavour to force their afcent to the fame height 

 from which they defcend, wherever they can find a 

 vent. 



As all the water which falls in rain has undergone a 

 natural did illation, it is much more pure when it firfl 

 falls, than after it has pafled through different ftrata of 

 the earth and riles in firings. Spring water is always 

 {bund to contain fome foreign admixture; if this fhould 

 be only an earthy fait, the water is called hard ; if it 

 contains other fubftances, it then receives the denomi- 

 nation of mineral water ; but thefe will require to be 

 treated of in a diftinc~t chapter. 



The water which lies upon marfhes and fwampy 

 grounds, has generally its fource in fome fpring, which 

 is placed above the level of the marfh. The foil, 

 therefore, in thofe places, being generally of a fpongy 

 texture imbibes the water, and permits it to difperfc 

 through its whole mafs, rather than force its way 

 through a certain aperture j and as marfh lands are 



commonly 



