Analogous Chemical Actions May Take Place In Primitive And Transition Slates As Well As In Tertiary Formations.

All slates, and this fact is very important, contain nearly five per cent of potash, sulphuret of iron, peroxide of iron, carbon, etc.

The contact of so many moistened heterogeneous substances must necessarily lead them to a change of state and composition. The efflorescent salts that abundantly cover the aluminous slates of Robalo, show how much these chemical effects are favoured by the high temperature of the climate; but, I repeat, in a rock where there are no crevices, no vacuities parallel to the direction and inclination of the strata, native alum, semitransparent and of conchoidal fracture, completely filling its place (its beds), must be regarded as of the same age with the rock in which it is contained. The term contemporary formation is here taken in the sense attached to it by geologists, in speaking of beds of quartz in clay-slate, granular limestone in mica-slate or feldspar in gneiss.

After having for a long time wandered over barren scenes amidst rocks entirely devoid of vegetation, our eyes dwelt with pleasure on tufts of malpighia and croton, which we found in descending toward the coast. These arborescent crotons were of two new species,* very remarkable for their form, and peculiar to the peninsula of Araya. (* Croton argyrophyllus and C. marginatus.) We arrived too late at the Laguna Chica to visit another rock situated farther east and celebrated by the name of the Laguna Grande, or the Laguna del Obispo.* (* Great Lake, or the Bishop's Lake.) We contented ourselves with admiring it from the height of the mountains that command the view; and, excepting the ports of Ferrol and Acapulco, there is perhaps none presenting a more extraordinary configuration.

Enter page number Go  Previous Next
Page 179 of 635
Words from 48935 to 49231 of 174507