499 



those who proceed in an opposite direction often throw doubt and 

 confusion upon the simplest phasnomena, as has sometimes happened 

 in an analogous case, when geologists have begun with the exami- 

 nation of granite and granite veins, and have then endeavoured to 

 apply the ideas derived from this study to the trap rocks and vol- 

 canic dykes. 



Among the most interesting conclusions deduced by M. Fournet 

 from his examination of the mining districts of Europe, I may men- 

 tion the modern periods at which the precious metals appear to have 

 entered into some veins: thus, to select a single example, some veins 

 of silver of Joachimsthal in Bohemia are proved to have originated 

 in the tertiary period*. 



FOREIGN GEOLOGY. 



Among the researches into the geology of foreign countries in 

 which our members have been recently engaged, 1 have grea*- 

 pleasure in alluding to the labours of Mr. H. E. Strickland and 

 Mr. Hamilton in Asia Minor. These gentlemen first examined the 

 neighbourhood of Constantinople, and found on both sides of the 

 Thracian Bosphorus an ancient group of fossiliferous strata, con- 

 sisting of schistj sandstone, and limestone. From the character of 

 the fossils it is inferred that these rocks may probably be the equi- 

 valents of the upper transition or Silurian strata of England. The 

 shells belong to the brachiopodous genera Spirifer, Producta, and 

 Terebratula, with which the remains of corals and Crinoidea were 

 associated, and fragments of a Trilobite. 



The rarity of any fossiliferous deposits of higher antiquity than 

 the old red sandstone in any of the countries bordering the Mediter- 

 ranean, or indeed to the south of the Alps and Pyrenees, lends con- 

 siderable interest to this observation. In their way through France, 

 our travellers examined the well known region of extinct volcanos 

 in Auvergne, and afterwards found a counterpart to it in the Cata- 

 cecaumene, a district in Asia known by that name in the time of 

 Strabo, from its burnt and arid appearance. Some of the volcanos 

 in Asia are of very modern appearance, although no notice of their 

 eruptions falls within the limits of history or tradition. The vol" 



* See " Etudes," &c. Section 2, 



