374 Miscellanies. 



18. Depth of mines, — Kits piihl copper mine in the p^et 



Tyrol mountains, - - - - " 2764 



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



Guanaxuato, Mexico, • 2170 



Dnsolidated mines, Cornwall, - 1650 



( 



(silver,) 



Monkvveannouth colliery, Durham, - _ . ^ 1600 



Wheal Abraham mine, G 

 Eiton mine, Staffordshire. 



1410 

 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 

 Monkwearraouth 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 of the sea,) was, until 

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

 view.) 



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

 mountain of S]ieve Donard, which has long afforded beryl in con- 

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



1 



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 show^n 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. 



f^ 



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

 Zennich. — ^The principal pneumatic methods are~L 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- 



with 



gas 



measuring the volume of nitrogen which results from the reaction ; 

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



