Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/453

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INFLXmKCB OF MAGNETISM ON CBTSTALLIZATION^

would radiate from their centres in straight lines, but now being formed within the influence of the magnetic force, and having a tendency to arrange themselves at right angles to the direction of that force, they are bent, as in the following figure, into true diamagnetic curves. When the quantity of mercury employed is large in proportion to the silver to be precipitated, the silver arranges itself, amalgamating with the mercury, in an arborescent form ; but on examination it will be found that the same tendency to a curvilinear direction exists, as is more strikingly shown in the distinct crystallme forms.

Fig. 5.

14. If we place equal weights of the proto-nitrate of mercury over the poles of tiie magnet, the glass plate being filled with a solution of nitrate of silver, we get very distinct evidence of a similar diamagnetic arrangement By the action of the proto-salt of mercury on the nitrate of silver, a double sub-salt of mercury and silver results. This salt crystallizes in little tufts, and under magnetic influence these tufts arrange themselves in very synunetrical order. The salt being placed over the poles of the magnet, and the plate being filled with the solution of nitrate of silver, there is almost immediately the formation of the double sub-salt about the north pole, the first indication being very faint streaming white lines, which radiate at right angles to the line of magnetic force. These are immediately followed by circles, shown by a little clouding of the fluid, which form around the poles as in a series of waves, projected by a sort of pulsation from tiie magnet. The circles gradually extend, and at length opening at some point they spread off in curves as in tiie accompanying figure (Fig. 6.)

It will be seen on examining this figure that certain spaces, one along the axial line from the south to the north pole, and the other from the north, at right angles to it are left free of crystals ; and not only that a more abundant crop of crystals occurs around the north pole, but that the power of that pole is such as to overcome, and bend back the curves

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