the
cutting discovers circular bands of very small diameter, arranged with
regularity round one circular spot. These circles are frequently so
perfect that they appear to be traced by the compass, and consist of
two or three, seldom of a greater number. The first round is white ;
the second, black, green, red, blue or yellow ; the most rare are those
whose circles are at equal distance from the centre.
The tree, or dendrifica, agate, from the Greek δένδρον, a tree, is
that in which the material being formed in successive strata, it has
allowed access between the strata to metallic solutions, which, under
the pressure of the air, and by the solidification of crystals, remain
there in a metallic state after evaporation.
It is called tree agate when the enclosed pieces represent trees, and muscosa when
the pattern resembles flies : very seldom are these two phenomena
represented together on one piece. Agates are found containing
impressions of different plants, and of what appear groups of herbs,
bushes of box tree, and ramifications of various sorts. The tree agate of
the East is superior to that of Europe ; the beautiful polish which it
takes, and its natural brightness, contrast in a marvellous manner with
the dark-coloured ramifications. When the colour of the plants is red,
the agates are more valued, because more rare.
Figured agates are
greatly admired for the form of their spots. Towards the close of the
last century they were much in demand, and brought a high price, whence
they were eagerly sought for, and perhaps
