i^ M. Mohs on the Discovery of XIsefitlMineraU. 



position of a plane is determined, and we must make our- 

 selves well acquainted with the strike end dip of the reposi- 

 tory, and especially the latter, in order to ascertain its thick- 

 ness (which is not shewn by the length of the bore in it), and 

 to be enabled to form a correct opinion of other circumstances. 

 We make these three bores at measured distances from one 

 another, compare the resvilt which they afford with the ge- 

 neral relations of the stratification, and assure ourselves, if we 

 find that it so far corresponds with them as may be expected 

 in cases of this kind, by means of some bores placed in proper 

 connection with them, that this correspondence has not been 

 accidental. But if we should find that the position and di- 

 rection do not correspond properly with the other relations of 

 the stratification, by which, according to experience, we must 

 take for gi-anted that these repositories are also regulated, 

 generally speaking, and as a whole, but that they deviate 

 more or less considerably from them ; then we have to do 

 with bondings or slips, or other irregularities of stratification, 

 or with dislocations and faults, caused by backs (Biicken), and 

 intruding alternations, or in general by vein-like formations. 

 It is well known how many difficulties are caused to mining 

 operations by such appearances, and I need dwell upon them 

 no longer in this place. We must endeavour, with all dili- 

 o-ence. to become acquainted with the circumstances which 

 o-ive rise to them, and if we do not find easy and safe means 

 of setting them aside and rendering them harmless, we ought 

 rather to go out of their way. This is also to be done by bores, 

 and in many cases it will be advisable not to spare these, as. 

 notwithstanding all our foresight, often enough unexpected 

 circumstances intervene which increase the difficulty of min- 

 ing. A number of bores will also be foimd useful by making 

 us acquainted with the substances worth mining, and those 

 which are not worth it, and hence they are serviceable in a 

 variety of ways. Nevertheless, in causing these bores to be 

 made, especially where it is requisite to give them a consider- 

 able depth, and thereby to render them expensive, we must 

 '-0 to work with proper caution, and it requires much atten- 

 tion, and knowledge of the repositories, if we wish to obtain 

 the conviction that Ave have bored at the proper place, and 



