268 



EXTINCT VOLCANOS, ETC. 



TTppeb 



Gallery. 



Table-case 

 in Recess 6. 



165. — Nodule of clay ironstone. — From Magnano, north 



of Monte Cimino. 



166. — Grey sulphide of antimony. — From the hills near 

 the Alum Works on Mount Tolfa. 



167. Bitumen, with white limestone. — From Castro, in 



the Campagna. 



168. Bitumen (asriialte). — From the hill under the 



lighthouse of Sabina. 



169. — SuLniUR on pepertno, which has been decomposed 

 by sulphurous acid gas. — From the road to Albano. 



170. — Minute crystals of sulphite, on a rock composed 

 of felspar, augite, and mica, which has been decomposed by 

 sulphurous acid gas. — From a mass near Bracciano. 



171. Detached hexagonal prisms of rock crystal* 



("Tolfa diamonds" ') with double pyramidal terminations. 



From a rock near Tolfa. 



172. Quartz rock,* in which the rock crystals No. 171 



are found. 



173. — Chalcedonic quartz* 



■From a hill amongst the 



Alum 



174. — Semi-opal* (quartz resinite). 



175. — Concretionary and aluminous quartz rock,* with 

 small cavities, which are lined and filled with cubical and 

 octohedral crystals of alumstone. — Found in the hollows of 

 the rock; used for making alum at the Works at Tolfa. 



176. — Fluor spar * 



177. 



178. 



fi 



( 



)* withfi 



1 79. — Alumstone.* 



White 



180. — Alumstone.* — From the Basaltic Cavern. 

 181. — Alumstone.* — From the Castellina Cavern. 

 182. — Alumstone.* — From the Great Cavern. 

 183. — Siliceous alumstone.* — From the Great Cavern 



* Nos. 173 to 187 are from the neighbourhood of the Alum Works 

 at Tolfa, near Civita Vecchia. 



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