Geological Obfervations. 385 



the Pic de midi (one of the Pyrenees, lower 

 than Conlgou) fait of tartar remained dry 

 for an hour and a half, though it immediately 

 moiftened at the bottom of the mountain. 

 The vapor of marine acid was alfo inviiible 

 on the fummit. The eledlric and magnetic 

 powers were as ftrong as on the plain. 8 Roz. 



43- 



Of the Structure of Mountains. 



Mountains confidered as to their flru&ure, 

 are divided into intire> Jiratijiedy and confu- 

 fed. 



Intire mountains are formed of huge maf- 

 fes of ftone, without any regular fiffure, and 

 moftly homogenous ; they confift chiefly of 

 granite, fomedmes of gneifs, fhiftus, flagftone, 

 fandftone, limeftone, gypfum, porphyry, 

 ferpentine, or trapp. Some in Sweden and 

 Norway confift of iron. 



Stratified mountains are thofe whofe mafs 

 i^ regularly divided by joints or fiffures ; 

 thefe ftrata are confidered in relation to the 

 angle which their fiflures make with the ho- 

 rizon and meridian, with refpecT: to the former 

 they are called horizontal, rifmg, or dipping. 

 With regard to the latter, they are faid to 

 run to this or that point fo many degrees 5 

 G c they 



