ON CONGLOMERATED ROCKS. 



209 



of mica, roundish grains or crystals of felspar, 

 and apparent fragments of different kinds: and 

 all of them are connected together either by means 

 of a clayey, calcareous, or quartzy basis, or are 

 immediately joined together without any cement 

 or basis, as is the case in granite. It is a very 

 frequent and abundant rock, and occurs in the 

 form of strata, beds, and veins, along with lime- 

 stone, gypsum, slate-clay, coal, and other mine- 

 rals. 



3. Trap-Tuff. 



Trap-tuff is composed of masses of basalt, amyg- 

 daloid, greenstone, wacke, felspar, clinkstone, trap- 

 tuff, limestone, sandstone, brown -coal, &c. im- 

 mersed in a basis of trap, which is sometimes of 

 the nature of basalt, sometimes of the nature of 

 wacke. It is associated with flcetz- trap rocks, and 

 is very frequent and abundant in the middle di- 

 vision of Scotland. 



Section II. 



THE MODE OF FORMATION OF CONGLOMERATED 

 OR BRECCIATED ROCKS. 



Let us now enquire whether these conglome- 

 rated rocks are Chemical or Mechanical forma- 

 tions. 



VOL. II. ® 



