certain Metalliferous Bepositories in Depth. 231 



whole of these veins belonging to the same set, and that it 

 is more rational to suppose that the differences of composi- 

 tion are owing to contemporaneous actions which alone could 

 operate with so much force, and with the exception of a single 

 vein. 



These anomalies, of which we could multiply examples, 

 must necessarily throw some uncertainty on the theoretical 

 conclusions generally adopted. In order to come to some de- 

 termination, let us penetrate into the interior of some repo- 

 sitories which may be cited as types of important altera- 

 tion in the superior parts, and study the details of this altera- 

 tion. 



The vein of Kautenbach, on the right bank of the Moselle 

 (province of Hunsdriick), is, like those of Berncastel, in whose 

 neighbourhood it lies, a plumbiferous vein with veinstone 

 {gangue) of quartz. All the superior part of this vein, to a 

 depth which is, at certain points, upwards of 60 yards from 

 the surface, abounds in yellow phosphate of lead, which has 

 long been the normal mineral as well as the galena. The 

 thickness of the compact or crystalline phosphate exceeds at 

 many points 060 ; and, although it is impossible to calculate 

 the quantity of phosphate furnished by this vein from the 

 time when it began to be mined, we may still affirm that it 

 may be reckoned by hundreds of cubic yards. In 1846, very 

 considerable quantities of these phosphates continued to be 

 extracted, although the chantiers were 60 yards from the sur- 

 face, and I could make the following observations on these 

 minerals : — the phosphate was compact, brown or yellowish- 

 white, and furrowed with crystalline drusy cavities, like a sul- 

 phuretted mineral. In many places the phosphate was ulti- 

 mately mingled with galena, and still more frequently the 

 crystals of phosphate from 0™-005 to 0^*020 in diameter, 

 perfectly formed, were embedded in the galena. Lastly, the 

 galena was still found in stalactites, covering the crystallised 

 gi'oups of the phosphate, and even the hexaedral crystals of 

 galena, were changed into phosphate. 



This intimate penetration of the two combinations prevents 

 us supposing that the phosphates of lead are posterior to the 

 galena, and result from its decomposition. Whence could 



