170 ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 



Acids. Sulphuric, nitric, silicic, hydrochloric. 



Semi-metals. Arsenic, antimony. 



Saloids. Chlorine, bromine, iodine, fluorine. 



Alkaline-metals. Potassium, sodium, lithium (ammonium), 

 rubidium, caesium. 



Alkaline Earths (metals of). Calcium, magnesium, barium, 

 strontium, aluminium, cerium, beryllium, yttrium, zirconium, 

 didymium.] 



Heavy Metals. Iron, cobalt, nickel, chromium, uranium, 

 vanadium, copper, lead, zinc, tin,* titanium, tantalum, molybdenum, 

 wolframium, bismuth. 



JVohle Metals. Gold, silver, mercury. 



The well-known examples of metallic and other minerals 

 formed since the time of the Roman occupation by the thermal 

 waters of Bourbonne les Bains, originally studied and reported 

 on by Daubree,! are particularly instructive. 



No fewer than 24 species of minerals were formed by the 

 issuing waters, among which were such well-known Cornish 

 species as iron pyrites, vivianite, anglesite, cerussite, galena, 

 chalcocite, covellite, chalcopyrite, erubescite, fahlerz, and cassiter- 

 ite, besides phosgenite and a number of zeolites — some deposited 

 by the waters itself and others formed by its action on bronzes and 

 works of art. The late Sir Warington Smyth, formerly one 

 of our Vice-Presidents, referring to this wonderful collection of 

 minerals of modern formation, said in his graphic way, 

 " Here we have — within a few yards of the surface and under a 

 very moderate temperature, the metals and alloys which had 

 been produced by human industry ; which had been raised by 

 the miner and altered by the hand of the metallurgist, brought 

 again to the identical compounds which we are accustomed to see 

 side by side in their original repositories, — fathoms and fathoms 

 deep underground. § 



* Tin has only been found in a few instances, the proportion heing from 

 "0000015 to "00000008 per cent, of the water. In Cornwall however the waters 

 flowing through the valley gravels must have contained tin in solution in compar- 

 atively recent times, if indeed they do not still ; since deer's antlers have been 

 found permeated with that metal. See Trans. E.G.S.C., Vol. x, and "Cornish 

 Tinstones," p. 33. 



t The metals in italics are perhaps doubtful. 



XFormation contemporaine de diver ses especes Minerales, Paris, 1876. 



§ Smyth, Presidential Address, Trans. Eoy. Geol. See. Corn., 1876. 



