AGATE. 
415 
Although agates may be said to be found in al- 
most every part of the world, yet there are some 
places particularly famous for them ; and one of the 
chief of these is Oberstein, in the Palatinate. The 
agates from this place are spread all over Europe, 
and are best known in mineralogical cabinets. They 
are found in hills composed of antient lava, the ex- 
terior part of which is decomposed, and resembles a 
mixture of clay, chalk, and oxide of iron. 
Agates which are not more than three or four 
inches in diameter are generally quite solid, and 
often exhibit, when cut, concentric zones of several 
colours. These zones approach more or less to the 
circular or oval shape, and very frequently are so 
irregular as somewhat to resemble the plan of a 
fortification. When the balls of this stone are of a 
considerable size, they are mostly hollow, and the 
cavities are sometimes very beautifully lined with 
crystallized pyramids of amethyst. On these cry- 
stals are often implanted hexahedral columns of cal- 
careous spar of a grayish colour, forming altogether 
the most beautiful group imaginable. 
Some of these hollow balls of the smallest size 
have their cavity filled with water, from whence 
they have obtained the name of enhydres. They 
are found in the territory of Vicentino in Italy, in 
the middle of a volcanic hill. These little agates, 
which are not much larger than an almond, contain 
a drop of water which never entirely fills the cavity, 
as it may be seen to move when the stone is turned 
between the fingers. 
