NOME VII. VOLCANIC itf TRITE. 



ramids of three sides, joined at the centre, with 

 diverging rays ; their bases forming the surface of 

 the circumference, but they are often covered with 

 a spherical layer of the same substance, confusedly 

 crystallised. Such are seen in the lavas of Murgo, 

 between Simeto and Lentini ; in the Rocks of the 

 Cyclops; and I have found them, from four to 

 six lines in diameter, in the vesicles of the lava 

 which is scattered in fragments on the chalky 

 mountain of Cifali, near Catania, where they 

 form curious fans when gently broken. 



" But more commonly this calcareous sub- 

 stance lines the cavities under the stalagmitic 

 form, in the shape of hanging crystals, or im- 

 planted globules. I have beautiful specimens 

 collected to the west of Lentini : some of the glo- 

 bules are void, the inner surface being only crys- 

 talised in what was formerly called the dogs-tooth 

 spar, but now the metastatic of that diligent crys- 

 talographer Haiiy. Under the same form these 

 spars line the cavities of the beautiful tufo around 

 Cape Passaro, formed of fragments of lava and 

 limestone, and many masses of lava alone ; and 

 in the rocks of the Cyclops it is not only found in 

 the cavities, but forming layers above the lava, 

 and even above the stratum of marl which covers 

 these famous rocks. 



" This substance is still more frequent in the others. 



