204 COSMOS. 



the deposition of the dissolved elements. By changes of pres- 

 sure and temperature, by internal electro-chemical processes, 

 and the specific attraction of the lateral walls (the rock tra- 

 versed), sometimes lamellar deposits, and sometimes masses 

 of concretion are produced in fissures and vesicular cavities. 

 In this way druses and porous amygdaloids appear to have 

 been sometimes formed. Where the deposition of the veins 

 has taken place in parallel zones, these zones usually 

 correspond with each other symmetrically in their nature 

 both vertically and laterally. Senarmont has succeeded in 

 preparing a considerable number of minerals artificially, by 

 perfectly analogous synthetical methods. 69 



One of my intimate friends, a highly endowed scientific 

 observer, will, I hope, before long publish a new and impor- 

 tant work upon the conditions of temperature of springs, and 

 in it treat with great acumen and universality, by induction 

 from a long series of recent observations, upon the involved 

 phenomenon of disturbances. In the determinations of tem- 

 perature made by him in Germany (on the Rhine) and in Italy 

 (in the vicinity of Rome, in the Albanian mountains and 

 the Apennines) from the year 1845 to 1853, Eduard Hall- 



59 Very important metalliferous lodes, perhaps the greater number, 

 appear to have been formed by solution, while the veins filled witn 

 concretions of metal seem to be nothing but immense canals more or 

 less obstructed, and formerly traversed by encrusting thermal waters. 

 The formation of a great number of minerals which, are met with in 

 these lodes, does not always presuppose conditions or agents very far 

 removed from existing causes. The two principal elements of the most 

 widely diffused thermal waters, the alkaline sulphurets and carbonates, 

 have enabled me to reproduce artificially, by very simple synthetic 

 methods, 29 distinct mineral species, nearly all crystallised, belonging 

 to the native metals (native silver, copper, and arsenic), quartz, specular 

 iron, carbonates of iron, nickel, zinc, manganese, sulphate of baryta, 

 pyrites, malachite, copper pyrites, sulphuretof copper, red arsenical and 

 antimonial silver. . . . We approach as closely as possible to the pro- 

 cesses of nature, if we succeed in reproducing mineral? in their conditions 

 of possible association, by means of the most widely diffused natural 

 chemical agents, and by imitating the phenomena which we still see 

 realised in the foci in which the mineral creation has concentrated the 

 remains of that activity which it formerly displayed with a very dif- 

 ferent energy" (H. de Senarmont, Sur la Formation des Mineraux pa,'.' 

 la Voie Humide, in the Annales de Chemie et de Physique, 3eme sdrie 

 t. xxxii, 1851, p. 234 ; see also Elie de Beaumont, Sur les Emanations 

 Volcaniques e\ Metalliferes, in the bulletin de la Societe Geologique dt 

 France, 2e &e"rie, t. xv. p. 129). 



