As fast as we descended, the succession of beds forming the primitive foundation came out with increasing distinctness. Geologists consider this primitive matter to be the base of the mineral crust of the earth, and have ascertained it to be composed of three different formations, schist, gneiss, and mica schist, resting upon that unchangeable foundation, the granite.

Never had mineralogists found themselves in so marvellous a situation to study nature in situ . What the boring machine, an insensible, inert instrument, was unable to bring to the surface of the inner structure of the globe, we were able to peruse with our own eyes and handle with our own hands.