MODE V. PORPHYRY. 



felsite is in that of lava with a base of siderite. It 

 is surprising that the French mineralogists have 

 not adduced this circumstance in favour of the 

 volcanic origin of basal tin. Clink-stone however 

 lias no sort of relation to the family of basalts, as 

 the chemical analysis infallibly demonstrates ; for 

 it only contains 3 in the 100 of iron, while all the 

 other modes present more than 20. It is there- 

 fore here classed under Felsite, with which the 

 analysis strictly corresponds, except that there is 

 double the quantity of iron, which imparts the 

 black colour. 



MODE V. PORPHYRY. 



This rock belongs to the division here called Name. 

 Int rites, as consisting of crystals or grains im- 

 bedded in a base or paste, in contradistinction 

 to Granites formed by simple coherence, and to 

 Glutenites, (both also derived from the Latin), in 

 which the particles are cemented together by 

 the same or by a different substance, scarcely 

 visible, or at least not so abundant as in the 

 Intrites*. This last denomination, besides in- 

 stantly recalling to memory the nature of the 

 rock, would prevent the misapplication of the 



* In like manner the Glandulites of Saussure are those stones 

 which include glands or kernels. 



TTNTVFPRTTV 



