NOME VIII. VOLCANIC GLUTENITE. 505 



some instructive remarks and interesting singu- 

 larities : and the extreme minuteness of the de- 

 scriptions will serve fully to instruct the reader 

 in the nature of these complex substances, the 

 mingled products of fire and water*. 



<c Division 1. Bricias, whose formation is Catalogue by 



Faujas. 



owing to lavas, which in their state of fluidity 

 have embraced other kinds of lavas, whether com- 

 pact or porous, scorified, vitreous, or other stony 

 substances reduced into fragments. When the 

 substances thus imbedded present kernels more or 

 less angular of a certain size, and the lava which 

 unites them is hard and solid, they may be called 

 volcanic bricias. If, on the contrary, the frag- 

 ments are very small, and the paste which sur- 

 rounds them is friable, soft, and rather earthy 

 than stony, the name tufo is more applicable. 



<c 1. Volcanic bricia, formed of angular and From fire, 

 round fragments of black compact lava, of black 

 lava rather porous, and some grains of white fel- 

 spar, strongly united by a very hard granular 

 lava, of a reddish colour. 



" 2. Bricia, formed of angular fragments of 

 black lava, hard, with small pores, united in a 



* This is also from the Annales du Museum. In the Geologir, 

 priginaUy delivered as a course of lectures, it is much abridged. 



. r 



