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 Faults 
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 
Pans, raising water to supply a Canal basin, from 
two strata at different depths. The water from 
the lowest stratum rises to the greatest height. 
See V. I. p. 562. Note. (Hericart de Thury.) 
which they were determined by the electric currents ” 
r.xiT.T;.!’;!’..'''''''”' 
« 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 
nietals 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.” 
of Tin when a solution of muriate 
toJLf] a portion of the metal is de- 
termined towards the negative pole, whilst another portion in the 
suite 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 nietals also very commonly occur to- 
gether in the same vein. ^ 
