Geological Society, -"^r-v ^q^ 



logical structure, embracing the transition and secondary rocks of 

 the Hartz, Thuringerwald, and Lower Rhine. In the larger map 

 all the tertiary and alluvial deposits are represented by one colour, 

 the author having never entered upon the subdivision and classifi- 

 cation of these formations. He had studied, however, the newer 

 secondary formations, which were depicted by several distinct 

 colours, and their history would have been included in the work 

 above alluded to, had he not been interrupted by his tour in Italy 

 and Sicily in 1830. 



Among his other writings, I may enumerate an Account of Mag- 

 deburg, Halberstadt, and the adjoining territory, and various papers 

 which will be found scattered through the journals of Poggendorff 

 and Karsten, the Hertha, and other German periodicals. The only 

 fruits which we as yet possess of the scientific expedition sent by 

 the Prussian Government under Hoffmann's direction to Italy and 

 Sicily, are some letters written by him during the journey, and an 

 excellent Memoir on the Lipari Islands ; and a valuable work by 

 one of his companions. Dr. Philippi of Berlin, who published in 

 Latin a detailed account of the recent testacea of Sicily, and the 

 tertiary fossil shells collected in the course of the expedition*. 



From Hoffmann's letters it clearly appears that the novelty of the 

 volcanic and tertiary phaenomena of Southern Italy and Sicily had 

 made a deep impression on his mind. He had been astonished, on 

 recognising the identity of the modern trap rocks of the Val di 

 Noto with those of ancient date in Germany, and the no less striking 

 similarity of the Siciliant ertiary limestones, containing recent shells 

 to many calcareous secondary formations of northern Europe. The 

 Lipari Islands afforded him a field for the examination of modern 

 igneous rocks, and the slow effects of volcanic heat in modifying 

 aqueous deposits. The picture which he has given of the fumeroles 

 of the western coast of Lipari, the principal island of the group, is 

 graphic and highly instructive. At St. Calogero numerous fissures 

 are seen permeated by heated vapours which are charged with sul- 

 phur, oxide of iron, and other minerals, in a gaseous state. Here 

 the tufaceous and other rocks are variously discoloured wherever 

 the steam has penetrated, and are sometimes crossed with ferrugi- 

 nous red stripes, so as to assume a chequered and brecciated ap- 

 pearance. In one place a felspathic lava lias been turned by the 

 vapours into stone as white as chalk marl, in another, a dark clay 

 has become yellow or snow-white, and these effects are not limited 

 to a small space, but are seen extending for four miles through ho- 

 rizontal strata of tuff, which rise occasionally to the height of more 

 than 200 feet. The greater part however of the alterations are re- 

 ferred to what are properly called extinct fumeroles, or the action 

 of volcanic emanations which have now ceased, but which must at 

 one period have resembled those of St. Calogero. Some of these 



♦ Philippi, " Enuincratio Molluscorum Siciliae turn viventium turn in 

 tellure tertiaria fossilium, quoc in Itinere suo observavit Auctur." 280 pages 

 4to, and 12 lithographic plates, Berlin, 1836. 



