C. G. Gmelin o)i Clinkstone or PhonoUte. 69 



ments, illustrative of the nature of the different kinds of clink- 

 stone. Our limits preclude us from giving more than the fol- 

 lowing, which are concluding inferences and questions. 



1. It follows, from the preceding investigations, that the 

 clinkstones of the Hegau, as also those of the Rhongehlrge, 

 are intimate combinations of mesotype and fehpai: In the 

 clinkstone of the Hegau, the mesotype preponderates over the 

 felspar, whilst in that of the Rhongebirge, the mesotype is al- 

 most excluded by the felspar, thus rendering it a nearly pure 



felspar rock. 



2. Although we cannot expect, in a compound of this de- 

 scription, that the constituent parts should occur in the same 

 determinate proportions, as in an individual formed by the 

 power of crystallization, it is worthy of notice that the differ- 

 ences are not considerable. When we view the constituent 

 parts of mesotype (exclusively of the water, which is always in 

 less quantity than in crystallized mesotype, owing to its being 

 intermixed with a foreign matter), we find that the fixed con- 

 stituent parts agree very nearly with what occurs in crystaUized 

 mesotype. The mesotype mass, in its composition, approaches 

 sometimes more to natrolite, sometimes more to raesolith, meso- 

 hne, &c. The felspar mass approaches very nearly in chemical 

 nature to the crystallized felspar : The following formula will 

 express its constitution. 



^ is^ + SAS^. 

 N j 



In a chemical view, the felspar bears nearly the same relation 

 to orlhoclase, as perecline to albite, and hence arises the ques- 

 tion, whether or not the glassy felspar which occurs in clmk- 

 stone, notwithstanding its agreement in form with orthoclase, be 

 not distinguished from it by a considerable dose of natron ? 



3. We can infer, with considerable certainty, from the speci- 

 fic gravity of the clinkstone, the proportion of mesotype to fel- 

 spar, it being a fact that the specific gravity diminishes as the 

 <iuantity of mesotype increases. This may indeed apply to all 

 zcolitic"compounds, in so far as these possess a lower specific gra- 

 vity than felspar. The clinkstone of Hohcnkiaiicn, in which the 

 mcsotypic mass predominates, has a specific gravity of 2.504; 



