115 



TAB. CLX. 



SILEX Quartzum ; var. 

 Quartz, or Agate, 



Class 2. Earths, Order 1. Homogeneous. 



Gen. 4. Silex. Spec. 1. Quartzum. 



Div. 2. Imitative. 



1 he river Tay in Perthshire, as well as other parts of 

 Scotland, affords many beautiful pebbles, with circles and 

 centres with more or less of the appearance of eyes, 8cc. 



The upper one has been cut for ornament, and was a present 

 from Lady Wilson to her daughter Lady Arden. The lower 

 specimen came from the Tay above mentioned, and was 

 lent me by my friend G. Laing, Esq. These pebbles ap- 

 pear to be formed in the rocks in short stalactites forming 

 in coats, which being more or less coloured by Oxide of 

 Iron, form stripes or circles, &cc; the outside rather 

 knobby. This the lapidaries have taken advantage of, as is 

 seen in these pebbles, and it assists in the disposition of 

 the colours. Much seems to depend upon Quartz, Alu- 

 mine and Iron to increase the beauties of this stone, 

 forming in it Jasper, Agate, Cornelian, &c, so arranged 

 in one stone as to give it variety and beauty *. The parts 

 with greenish specks, which are magnified a little at the 

 bottom, are more porous than the rest, apparently filled 

 with Chlorite. 



* The red circles are often specks of red in transparent Quartz. 



