M. Mohs on the Discoverij of Useful Minerals, 339 



tudinal ranges, are parallel or nearly so, and which generally 

 terminate in the' longitudinal valleys, or in plains at the foot of 

 the mountains, cutting, for the most part, almost at right 

 angles the direction of the mountain-ranges, and the stratifi- 

 cation and structure of the mountain-masses. Whoever has 

 studied attentively the relations of the surface and the rela- 

 tions of the stratification of mountains in nature (not according 

 to any system merely found in books), knows what modifications 

 and deviations are to be expected in respect to the right- 

 angled union of the descending lateral chains with the princi- 

 pal chain, and in respect to the parallel position of the valleys, 

 and hence this requires no further consideration ; but another 

 character seems not to be superfluous in this place, which 

 is, that we must not from what we have observed on one de- 

 clivity, in reference to the relations we have been discussing, 

 form our conclusions as to what may be presented by the other, 

 without having previously seen and examined it ; because the 

 two declivities of a mountain-range are not unfrequently much 

 more different, in every respect, than certain assumptions, espe- 

 cially the precipitation theory, generally represent them to be. 

 As to the transverse valleys, although not one of them 

 ought to remain uninvestigated, yet a proper selection must be 

 made, in order that we may commence wth that one which 

 promises to afford the most information, and which is there- 

 fore likely to assist and facilitate our search to the greatest 

 extent. The selection of such a transverse valley can only be 

 made hy those who, in the manner above described, have ac- 

 quired a perfect and personal knowledge of the whole district. 

 In general, it may be anticipated that such a valley will be 

 found in the centre of the mountains, and will be that one 

 which penetrates most deeply into their mass, and which 

 reaches farthest into the high mountain-ranges ; which cuts the 

 stratification and rocky structure most nearly at right angles, 

 and whose declivities present the most numerous and best 

 opportunities of making observations by means of the nume- 

 rous exposures on their sides, and also by their lateral val- 

 leys and ravines. These are all relations which can be easily 

 percciveJ, and whicJi must be well considered before we be- 



