PROCEEDINGS 1849 — 1858. 
270 
clay was dried, and was found to be indurated in a remarkable 
manner on one side of the plate, whilst on the other it was laminated, 
the clay breaking off in thin shales ; the depth to which this lamina- 
tion extended being determined by the length of time the clay was 
under Voltaic influence. The hardening on the other side was found 
to be due to the formation of small concretions arranging themselves 
along tolerably well defined curved lines. Results of this kind appear 
to show that electricity exerts some powerful influence on the par- 
ticles of matter grouping themselves in the crystalline rocks, and that 
concretionary nodules, such as are not unfrecpiently found in lime- 
stone or laminated stone, may be the result of position in regard to 
the line along which the force of the current of electricity may be 
acting. In connection with the mineral deposits, all the productive 
copper mines of Cornwall are found at the juncture of granite and 
clay-slate, with a main direction from north-east to the south-west. 
The lead lodes of Yorkshire and the Xortli of England indicate a set 
of rock conditions of a similar order. At Alston Moor, which Mr. 
Hunt had recently examined, he found that the lead occurred 
in different la3^ers of silicious sandstones, limestones, and clays, 
and that the amount of lead depended to a large extent on 
the rock through which the vein passes. In the silicious rock 
the vein is small, and contains but little lead ore ; in the argil- 
laceous there is frequently none ; but in the Hmestones it occurs 
in great abundance. The electricity developed by mineral veins had 
been investigated by Mr. Fox, Mr. Henwood, Mr. J. A. Phillips, and 
Mr. Hunt, and they found by connecting two parts of a lode by 
copper wires to a galvanometer the needle was powerfully deflected, 
and in some cases it swung round with extraordinary violence. This 
the author concluded was due to electrical changes going on within the 
lode itself That electricity has considerable influence on the forma- 
tion of mineral lodes, he demonstrated by an experiment which he 
described ; a quantity of clay, in the condition of thin cream, was 
mixed with a solution of sulphate of copper, and placed between 
a properly adjusted voltaic pair, which were kept in a state of excite- 
ment for more than a 3^ear ; the water was then evaporated and the 
mass hardened, and in addition to the lamination and induration 
