explanation of plate 68. 
109 
Plate 68. V. I. p. 563. 
Section shewing the basin-shaped disposition of Strata 
6 onging to the Tertiary and Cretaceous Formations, in 
'e Basin of London, and illustrating the causes of the 
“■ise of water in Artesian Wells. See V. I. p. 564. Note. 
(Original.) 
srvaLle in them? Copper, Tin, Iron, and Zinc, in combination 
tlie sulphuric and muriatic acids, being very soluble in water, 
in this state, capable of conducting voltaic electricity ; so, if by 
®eans of infiltration, or any other process, we suppose the water 
ro impregnated with any of these metallic salts, the 
^ocks containing different salts would undoubtedly become in diffe- 
®llt or opposite electrical conditions ; and hence, if there were no 
er cause, electric currents would be generated, and be readily 
ansniitled through the fissures containing water with salts in solu- 
‘°11; and decompositions of the salts and a transference of their 
® einents, in some cases, to great distances, would be the natural re- 
11 1. Butj on the known principles of Electro-nnignetism, it is evi- 
®iit that such currents would be more or less influenced in their 
^irection and intensity by the magnetism of the earth. They cannot, 
gi iii®lance, pass from N. to S. or from S. to N. so easily as from 
^ • to \V. but more so than from W. to E. The terrestrial magne- 
®in would therefore tend, in a greater or less degree, to direct the 
aic currents through tliose fissures which might approximate to 
east and west bearing, and in separating the saline constituents, 
ii'ould deposit the metal witliin or near the electro-negative rock, 
und the acid would be determined towards the electro-positive rock, 
pi obably enter new combinations. Or, the sulphuric acid might, 
means of the same agency, be resolved into its elements ; in which 
ase tlie sulidinr would take the direction of the metal, and the ox- 
ygen of the acid, nnd in this way, the metallic sulphurets may have 
probably their origin ; for, if I mistake not, the metallic sulphates, 
Pposing them to have been the prevailing salts, as at present, 
^ould be fully adeiiuatc to supply all the sulphur required by the 
ded^ *0 form sulphurets; indeed more fhau sufficient, if w'e 
uct the oxyde of tin, and other metalliferous oxydes found in our 
continued circulation of the waters would, in time, 
till of soluble salts under the influence of these currents, 
the metals were in great measure separated from their solvents. 
