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have been similar, but considerable differences of opinion 
have prevailed as to the origin of the electricity detected. 
The mode of examination was to connect with two lodes, 
or with separate parts of the same lode, copper wires, which 
were brought in contact with a galvanometer. In nearly all 
cases the galvanometric needle was most powerfully deflected, 
and, in some cases, swung round with extraordinary violence. 
Mr. Fox is disposed to consider these currents as the 
electric current which exerts its disposing power on the 
mineral lode itself. My conclusion is, however, that 
it is due to changes going on within the lode itself. 
Since, when a mineral lode is much decomposed, 
the deflection of a heavy needle is produced with con- 
siderable force ; but when, on the contrary, a lode is 
very solid, the electricity detected is very slight, and 
indeed, in lead lodes, where decomposition is far less 
frequent, the electricity, if there be any free, is insufficient to 
move a very sensitive galvanometer. Mr. R. W. Fox, and 
Mr. Thomas Jordan showed, many years ago, that by 
placing a wall of clay between a galvanic pair, and supplying 
some solution of sulphate of copper to it, a well-defined 
miniature mineral lode was formed at right angles to the 
direction of the electric current. Experiments of this class 
have been repeatedly made, and with a constant result. 
A quantity of clay in the condition of thin cream, having 
been mixed up with a solution of sulphate of copper, was 
placed between a properly adjusted voltaic pair, which were 
kept in a state of excitement for more than a year ; when 
the water was evaporated and the mass hardened, in addition 
to the lamination and induration already described, there was 
found a miniature mineral lode formed of the carbonate of 
copper, interspersed with the red oxide, and with, here and 
there, beautiful particles of native copper. 
Such are the evidences for and against the electrical theory, 
D D 
