481 



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 has 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 

 have produced veins of fibrous gypsum, calcedony, and opal, mi- 

 nerals which must have been introduced into the rents in a state of 

 sublimation. 



In some places there are tufaceous marls, regularly alternating in 

 thin beds, with still thinner and countless layers of granular gypsum, 

 the whole mass being again run through everywhere by irregular 

 branching veins of silky fibrous gypsum. These strata, thus inter- 

 sected, present a perfect counterpart to some of the secondary 

 gypseous marls, both of the keuper and variegated sandstone for- 

 mations in Germany*. 



When reading the Professor's description of these phaenomena, 

 we share in the pleasure and surprise which he felt on comparing 

 strata of high antiquity with others of so recent a date, and which, 

 moreover, owe a portion of that resemblance to changes now daily 

 in progress. 



The writings of Baron Daudebard de Ferussac were not devoted 

 principally to Geology, but we are indebted to him for several me- 

 moirs, and among others for an Essay, published in 1814, on fresh- 

 water formations, with a catalogue of the species of land and fresh- 

 water shells which were then known to enter into their composition. 

 Monsieur de Ferussac contributed largely to the Geological section 

 of the Bulletin Universel des Sciences Naturelles, a journal, of which 



* Liparischen Inseln, p. 41. Leipzig, 1832. 



