M. Mohs oil the Discover^/ of Useful Minerals. 841 



■masses, we must also combine the examination of the sand 

 which the rivers deposit in different portions of their vicinity 

 on sand banks, &c. and we must examine it not merely at its 

 surface, but as deep as it extends. The usual and well-known 

 methods are to be employed, and although neither gold nor 

 any other useful mineral be found, we sometimes obtain valua- 

 ble indications for the prosecution of our researches. 



We are now to proceed to the more minute consideration 

 of the two sides of the valley. We determine, in the first 

 moimtain-mass which presents itself to our observation, the 

 kind of rock, and its particular variety, and take specimens of 

 it, in order to institute a comparison with others. The direc- 

 tion and dip are to be ascertained with the greatest possible 

 accuracy, and also the extent, when the form and structure 

 admit of it. We have to investigate the structure of the 

 mountain-masses or that of distinct concretions, and we have 

 to consider attentively the sm*faces of the distinct concretions 

 {zusammensetzuyigs fldchen), to know if there are not other 

 rock-separations distinct from the surfaces of the distinct con- 

 cretions, and if these surfaces are separated by any inten^ening 

 substance such as loam, clay, or of any other mineral or mi- 

 nerals. If there should be such separating substances, we 

 ought to take specimens of as distinct a nature as can be ob- 

 tained. We should also not lea"\e unnoticed the minerals 

 foreign to the composition or nature of the rock, and which 

 occur either disseminated or in any other way distributed, 

 and should examfne the condition of the rock, as to whether 

 it is perfectly fresh, or if it has suffered a more or less 

 complete decomposition, either in whole or in part. The 

 cause of such decomposition is to be carefully investigated. 

 If we find that this change proceeds from a seam of the 

 rock, or a fissure, which is not an ordinary surface of a 

 distinct concretion, we are to follow this fissure so far as 

 is permitted by the exposure of the rock, and to observe 

 attentively what is presented by its continuation. This in- 

 vestigation is to be extended over the whole mountain-mass, 

 so far as it is accessible on the declivity, and an opinion is to 

 l>e formed regarding the portions which cannot be reached, 

 by moans of the fragments which have fallen down from thenr. 



