Chap. 14.] Jgate, C: / VW/*, &. 93 



carnelion, fomctimes diipofcJ in firata, and fometimes 

 confufedly blended and mixed together. Its colours 

 are therefore a mixture of white and red, fometimes in 

 itripes, fometimes irregularly notched. 



9. Agate. This name is given to flints that are va- 

 riegated wirh different colours promifcuoufly blended 

 together, and they are efteemed in proportion to the 

 mixture and perfection of their colours. 



10. Common flint or pebble, is in reality of the 

 fame nature with agate, bur wanting the beautiful and 

 various colours of the fubftances that bear that name. 

 Chalk and white lime-ftone are ufually the matrices of 

 flints, in which they are imbedded in the form of no- 

 dules, confiding of nuclei involved in a cruft. 



1 1. Chert is lefs hard and tranfparent than the com- 

 mon flint. It is not in general found in Icofeand fmgle. 

 irregular nodules, but forms veins in rocks. Cherts 

 are found of a flelH- colour, white, pale yellow, and 

 greenifh, and feem to be of an intermediate nature 

 between the flints and jafpers. 



Sand and gravel may be considered as flinty matters, 

 torn away from the rocks in which they originally ex- 

 ifted, and afterwards worn and fmoothed by the attri- 

 tion occafioned by the motion of water. Sand and 

 gravel, however, confiftof all the variety of flony mat- 

 ters which exifted in the mafies from which they pro- 

 ceeded, and are therefore found of many' different co- 

 lours and properties. 



IV. The name of JASPERS is given to all the opake 

 filiceous ftones, which in their texture refemble dried 

 clay. The -principal circumftance, befides their ap- 

 pearance, which diftinguiihes them from the other 

 Jiiiceous orders, is their more eafily melting in the 

 fire. They in general contain much iron. They are 



very 



