MODE III. BASALT1N. 



pact corneenne, but also to composite rocks, or 

 to rocks of which this corneenne forms the ce- 

 ment; it is the saxum trapezium^ Wall. Sp. 220. 

 We may also see the description that M. Nose 

 gives of 31 species of traps which he received 

 from Sweden, Bey tr age, p. 401. seq. M. de 

 Faujas, in his little treatise upon traps, equally 

 gives to this word a very wide acceptation; but 

 it does not seem conformable to the laws of a 

 good nomenclature, to give the same name to 

 substances which belong to different classes,, 



" It is according to these principles that 

 I determined to confine the name of trap to 

 a composite rock, or to the rock of which 

 I have given a definition at the beginning of 

 this paragraph. 



" 1946. The traps forming the cement of dif- 

 ferent variolites of the river Emme, vary in their 

 colours and nature. We see some of them grey, 

 others approaching to green, and others to a 

 violet colour ; they are more or less hard, some 

 containing only in their glands free calcareous 

 parts ; others contain in their paste some which 

 become friable after having remained in the ni- 

 trous acid. Even the cement which unites the 

 grains or small crystals of these traps is for the 

 most part clay, hardened into argillolite, more 

 or less ferruginous. The little grains, I speak 



