and Spouting' Fountams. 24S 



perfeetly sound chalk-masses, which are without fissures and 

 impermeable. If the piercer enters into one of these trenches, 

 water will gush up, more or less, according to the pressure which 

 it there sustains. If, on the other hand, the work is unfortu- 

 nately carried on in a very compact portion of the chalk, the 

 whole will be only labour lost. But in this there is nothing to 

 excite surprise. If, instead of expecting water in the interior, 

 or even in the upper part only of the mass of chalk, the sound- 

 ings were carried to the impermeable bed upon which this mass 

 rests, then there would be encountered not only streamlets, — not 

 only liquid trenches, but a plentiful reservoir ; and the success 

 of the operation would be in no degree doubtful. 



There exist certain localities, and the city of Tours is one of 

 them, where wells may be sunk, and approximated to each other, 

 almost indefinitely, without injury being done to any of them. 

 There are other places, on the contrary, where every new well 

 immediately produces a diminution of the issues of all the 

 others, or a lowering of their waters. But these differences will 

 not surprise those who have read with attention what has 

 been said above regarding the influence of the tides upon 

 these fountains. (See p. 283.) In truth, they will perceive that 

 in the former alternative, the sum of the openings by which the 

 waters ascend is very small, when compared to the extent of 

 the mass of water whence they spring ; and, in the latter, this 

 comparative smallness of the dimensions necessary to the steadi- 

 ness of the hydrostatic pressure, is not present. These pheno- 

 mena, therefore, are nothing more than a kind of experimental 

 verification of the hydrodynamic principles which we have al- 

 ready stated. 



The jets of two fountains in the paper manufactory of M. de 

 la Garde, near to Coulommiers, experienced a rise of more than 

 a foot and a half in the great drought of 1827, that is to say, 

 during a time when the great majority of common springs were 

 dried up. Although this state of things did not continue above 

 a few days, yet it is not the less remarkable. No satisfactory 

 explanation has yet been offered of it. I ought not, however, 

 to omit to add, that after this extraordinary appearance, the 



