Park. — Origin of Metal-hearing Solutions. 99 



solutions come in contact with rocks, flis work created a new 

 scientific basis of research in this branch of economic geology. 

 He contended that ores were obtained by leaching from the 

 rocks traversed by the veins, and suggested the possibility of 

 the vein-constituents being found in the adjacent rocks. 



In 1855 Forchhammer, the famous chemist of Copenhagen, 

 found traces of lead, copper, and zinc in the roofing-slates of 

 North Walesi a discovery which was held to afford conclusive 

 proof of the origin of ore- veins by processes of lateral secretion. 



In 1873 Professor F. Sandberger, of Wurzburg, dissatisfied 

 with the meagre results obtained from the examination of sedi- 

 mentary rocks, directed his attention to a systematic chemical 

 investigation of the rocks traversed by ore-veins, and of the 

 vein-stuff itself, in different mining centres in the Black Forest. 

 In clay-slate he discovered copper, zinc, lead, arsenic, antimony, 

 tin, cobalt, and nickel ; in sandstone, lead and copper. Titanic 

 and phosphoric acids were found to be present everywhere in 

 small quantity. 



Sandberger's results showed that a close relationship existed 

 between vein-contents and the country rock ; but he was by 

 no means satisfied as to the origin of the heavy metals. He 

 accordingly extended his investigation to an examination of 

 the constituents of igneous rocks. He crushed large samples of 

 rock and separated the constituent minerals by solutions of 

 different densities. Large samples of the individual crystallized 

 silicates thus isolated were subjected to careful analysis. In 

 this way he found all the usual elements formed in metalliferous 

 veins. Thus, in olivine he found iron, nickel, copper, and cobalt ; 

 in augite, copper, cobalt, iron, nickel, lead, tin, and zinc ; and 

 in the micas, many base metals. Gold, mercury, and tellurium 

 were not sought for. 



In 1880 Sandberger announced his belief that the mineral 

 contents of veins were derived not from some unknown depth, 

 but from the immediate wall-rock. 



Gold-bearing veins are common in slates and sandstones of 

 marine origin ; and, as sea- water, according to the announce- 

 ment of Sonstadt* in 1872, contains somewhat under a grain 

 of gold to the ton, it is held by the exponents of lateral secretion 

 that the sea is therefore the source of the gold in veins traversing 

 marine sedimentaries. It is maintained that when sediments 

 are deposited on the floor of the sea they must necessarily en- 

 tangle a certain proportion of sea-water, and that when these 

 sediments become consolidated the gold must remain in them. 



* Confirmed by Profes.ior Liversidse in 1893 and Su' William Ram.say, 

 F.R.S., in 1905. 



