transmitted through crystallized Bodies. 193 
I 
in their structure, the fibres stretching at right angles to the 
lamina2 through the whole of their thickness. 
These different structures will be better undc^rstood from 
fig. 1 and 2 of Plate V. Fig. 1, represents the specimen of 
agate with incurvated veins which I have noticed in a former 
paper.'^ It is composed of two veins, AB, CD, and three trans- 
parent portions AEB, ABDC, and CFD. The transpareiit 
portions exhibit the second variety of structure, though the 
small serpentine lines are not so distinctly marked as in other 
specimens. The two veins AB, CD, are both white when seen 
by reflected light. The breadtii of x\B is one-tenth of an 
inch and its radius of curvature inch, and it consists oifoiir 
smaller veins 7 nn, op, qr, xvx. The light reflected by mn is a paler 
white, and the light transmitted by it a lighter brown than in 
the other parts of the vein. The light which op reflects is of 
a brighter white, and that which it transmits of a deeper brown 
than in the other parts of the vein, and at the junction of mn 
and op there are several tufts of fibres of the same character 
as op. The other divisions of the vein qr and wx are of an 
intermediate character between m)i and op. The vein CD re- 
sembles the division mn, and possesses, like AB, the fibrous 
structure already described. The thickness of the plate AEDC 
is one- fiftieth part of an inch ; AC is three-tenths of an inch ; 
and a line AC forms an angle of about 25® with a plane per- 
pendicular to the laminae. 
Figure 2, represents another specimen of agate of a different 
character. It consists of transparent portions AB, BC, CD, 
DE, EF, separated from each other by white veins Bh, Cc, &c. 
and distinctly exhibiting the second variety of structure; and 
• See Phil. Trans. 1813, Part I. 
MDCCCXIV. C C 
