MODE VIII. ARGILLACEOUS GLUTENITE. 291 



of bricia, consisting of granite and other primitive 

 rocks. But this bricia seems to be united by a 

 siliceous cement : if the fragments be sometimes 

 joined by the argillaceous sand-stone, it may be 

 classed under this division. 



The substance called grauwack by the Germans Grauwack. 

 sometimes contains large fragments of clay slate, 

 and large pebbles of quartz ; but as its grain in 

 general is rather that of a sand-stone, it will be 

 considered under the next structure. The Ger^ 

 man name is not only barbarous in itself, but im- 

 plies grey wacken ; while wacken is a rock essen- 

 tially different. Mr. Kir wan says that it is the 

 grts-gris, or grey sand-stone, of the French, a 

 name very applicable ; and it seems also to be the 

 grison of some French topographers. The latter 

 appellation might be adopted as at once express^ 

 ive and sonorous; but as other important rocks 

 have received appellations from the illustrious 

 founders of mineralogy, the term Bergmanite may 

 perhaps be preferable. 



STRUCTURE II. SMALL-GRAINED ARGILLACEOUS GLU- 

 TENITE. 



The most celebrated rock of this denomination orison, or 



. u Bergmanite. 



is the Grison, or Bergmanite, just mentioned, 

 being composed of grains of sand, various in size, 

 sometimes even kernels of quartz; which, with 



u 2 



