110 EXPLANATION OF PLATE 69. 



Plate 69. V. I. p. 565. 



Fig. 1. Theoretical section, illustrating the Hydraulic 

 conditions of strata disposed in the form of Basins. 

 See Vol. I. p. 565, Note. (Original.) 



Fig. 2. Theoretical section, shewing the effect of Faulti 

 and Dykes on water percolating inclined and per- 

 meable Strata. See Vol. I. p. 566, Note. (Original.) 



Fig. 3. Double Artesian Fountain at St. Ouen, near 

 Paris, raising water to supply a Canal basin, from 

 two strata at different depths. The water fromwi 

 the lowest stratum rises to the greatest height. 

 See V. I. p. 562. Note. (Hericart de Thury.) 



and deposited in the East and West veins, and near the rocks to 

 which they were determined by the electric currents." 



In a Letter to the Author upon this subject (June 29, 1836), Mr, 

 Fox further remarks : 



'' It should be observed that in proportion as the deposition of the 

 metals proceeded, the voltaic action must necessarily have been 

 considerably augmented, so as to render it highly probable that the 

 metals were chiefly deposited at rather an early period in the history 

 of the containing veins ; and their intersection by other veins seems 

 to strengthen this probability." 



Mr. Fox has found by experiment that when a solution of muriate 

 of Tin is placed in the voltaic current, a portion of the metal is de- 

 termined towards the negative pole, whilst another portion in the 

 state of an oxide passes to the positive pole. This fact appears to 

 him to afford a striking illustration of the manner in which Tin and 

 Copper have been separated from each other in the same vein, or in 

 contiguous veins, whilst these metals also very commonly occur to- 

 gether in the same vein. 





