Page:Popular Science Monthly Volume 14.djvu/452

436 crystalline specks that the whole has the rounded appearance as in Fig. 3. The arborescent crystals that succeed the fringes, from a saturated solution, are smaller in their foliage than the last, and end in small spherical or botryoidal knobs.

Besides these various forms, there occur all kinds of crystalline combinations, as for instance the spray sketched in Fig. 4, when the long

and rough branches have terminated each in a large hexagonal plate and the flowing past of a weak solution has afterward caused the growth of delicate fern-leaves. Often, also, a large expansion will take place in every direction, though joined to the parent stem by an almost invisible thread; or, from the point of a long crystal there will branch out to right and left crescent-shaped structures, a process the commencement of which is seen in one of the side rays of Fig. 1. The last traces of silver will frequently give rise to delicate crystalline filaments wandering over the surface of the glass, as in Fig. 5.

If a piece of zinc be placed in a solution of neutral terchloride of

gold, containing about nine per cent, of salt, there is an immediate out-growth of black gold, which speedily changes to an advancing mass of yellow or perhaps lilac metal of lichen-like forms, from which proceed beautiful fringes of yellow or black, ending generally in such