148 



tufas* present in Italy, at Teneriffe, and in the 

 Andes. Thus it is by connecting in the mind 

 the primitive, secondary, and volcanic rocks, 

 and making a distinction between the oxidated 

 crust of the globe, and the interior nucleus, 

 composed perhaps of metallic and inflammable 

 substances, that we every where recognize the 

 existence of grottoes. They act in the cecono- 

 my of nature as vast reservoirs of water and of 

 elastic fluids. 



The gypseous caverns glitter with the splen- 

 dor of the chrystallized selenite. Vitreous 

 chrystallized plates of brown and yellow display 

 themselves in a striped ground composed of lay- 

 ers of alabaster and fetid lime-stone. The cal- 

 careous grottoes have a more uniform tint. 

 They are more beautiful, and richer in stalacti- 

 tes, in proportion as they are narrower, and the 

 circulation of air is less free. It is on account 

 of it's being too spacious, and too accessible to 

 air, that the cavern of Caripe is almost destitute 

 of those incrustations, the imitative forms of 

 which excite in other countries the curiosity of 



* Sometimes fire acts like water in carrying oft' substances : 

 and thus the cavities may be caused by an igneous, though 

 more frequently by an aqueous erosion or solution. Captain 

 Flinders, whose melancholy and untimely end the friends of 

 science deplore, attributes a cavern near the plantation JVJe- 

 nil in the Isle of France, to a mass of glance-iron melted 

 and carried away by a volcanic eruption. Voyages to Terra 

 Australis, vol. ii, p. 445. 



