342 M, Mohs on the Discovery of Useful Minerals. 



No exertion is to be spared, and we are to leave no pheno- 

 mena, however trifling they may seem, unobserved ; for who- 

 ever is acquainted with mountains to any extent, must be 

 aware how important for our present object, or even for purely 

 geological purposes, an apparently insignificant cu'cumstancc 

 may become.* 



After all this has been attended to, the superficial relations 

 represented on the map, and the other circumstances carefully 

 noted down, and after sufficient specimens have been collected, 

 we proceed to the next mountain-mass, if there should be 

 another present. If there be no other, that is, if the valley 

 lies, throughout its whole extent, in one and the same moun- 

 tain-mass, it happens not unfrequently that this mass presents 

 several varieties of I'ock, and many difterences in its structure 

 on the large scale. All such are to be observed, and we pro- 

 ceed with them exactly as we have already described. Of 

 course there must be lateral vallejs or ravines on the two sides 

 of the transverse valley with which we are occvipied ; and it 

 is plain that we must extend our investigations to all their 

 separate portions up to the summit itself of the mountain- 

 range, and thus attend to the position of such small notches, 

 as it is often less exactly laid down on the map than the posi- 

 tion of the larger valleys. It is not superfluous, also, to mark 

 in the enlarged copy of the map, the bendings, the enlarge- 

 ments, and the contractions of the valley. 



If, in the valley under investigation, there should occur a 

 series or alternation of several mountain-masses, the most im- 

 portant subjects for examination, after those already men- 

 tioned, are the boundaries between each two. These boun- 

 daries, or the surfaces of superposition, are generally somewhat 

 difficult to disco^■er, for they are seldom exposed, at least for 

 any considerable extent. They are generally covered by frag- 

 ments, or with earth or vegetation, or the rock is, in their vi- 

 cinity, much destroyed and decomposed ; and we are not un- 



* Such investigations teach us more especially that many of the pheno- 

 mena -which we observe, particularly in structure and superposition, cannot 

 be explained by general or partial, or by slow- or rapid and sudden eleva- 

 tions, or, in short, by mechanical causes, 



