374 Miscellanies. 



18. Depth of mines. — Kits piihl copper mine in the peet. 

 Tyrol mountains, - _ _ _ 2764 



Sampson mine at Andreasberg, in the Hartz, - - 2230 



Valenciana mine, (silver,) Guanaxuato, Mexico, - 2170 



Pearce's shaft, (copper,) consolidated mines, Cornwall, - 1650 

 Monkwearmouth colliery, Durham, _ ^ _ 1600 



Wheal Abraham mine, Cornwall, _ _ > 1410 



Eiton mine, Staffordshire, - - - - 1380 



The deep mines in the Tyrol, Hartz and Andes, above described, 

 are all in high situations — the bottom of the Mexican mine is six 

 thousand feet higher than the top of the Cornwall shaft. The 

 deepest perforation beneath the level of the sea, and consequently 

 the nearest approach to the earth's centre, has been made at the 

 Monkwearmouth colliery, which is fifteen hundred and thirteen feet 

 below the surface of the German ocean. Pearce's shaft (thirteen hun- 

 dred and thirty eight feet below the level o"f the' sea,) was, until 

 lately, the deepest in the world. — Geology in 1835, {Mining Re- 

 view.) 



19. Topaz in Ireland. — This mineral has been found in the 

 mountain of Slieve Donard, which has long afforded beryl in con- 

 siderable quantities. — Trans. Dub. Geo. Soc. Vol. I. 



20. Roasting of copper ores. — Hitherto the copper ores of Fah- 

 lun have been roasted in rectangular spaces, but some recent exper- 

 iments have satisfactorily shown that reverbatory furnaces are the 

 best. The ore must be reduced to the state of a coarse powder, in 

 which condition it requires only eighty hours for completing the pro- 

 cess. — Ann. du comptoir des mines de fer in Sweden. - 



21. The best method of assaying the ores of Manganese, by 

 Zennich. — 'The principal pneumatic methods are — 1. Calcination 

 and measuring the quantity of oxygen gas evolved ; 2. Ebullition 

 with concentrated sulphuric acid, and measuring the quantities of 

 oxygen ; 3. Calcination with sugar, and measuring the volume of 

 carbonic acid formed ; 4. Ebullition with muriatic acid, and measur- 

 ing the quantity of chlorine disengaged ; 5. Ebullition with muriatic 

 acid, and making the chlorine gas to react upon liquid ammonia, and 

 measuring the volume of nitrogen which results from the reaction ; 

 6. Calcination with sal-ammoniac, and measuring the gas evolved ; 



