I have said the Uspallata range is geologically, although only 6,000-7,000 feet, a continuation of the grand eastern chain.

It has its nucleus of granite, consists of grand beds of various crystalline rocks, which I can feel no doubt are subaqueous lavas alternating with sandstone, conglomerates and white aluminous beds (like decomposed feldspar) with many other curious varieties of sedimentary deposits.

These lavas and sandstones alterate very many times, and are quite conformable one to the other.

During two days of careful examination I said to myself at least fifty times, how exactly like (only rather harder) these beds are to those of the upper Tertiary strata of Patagonia, Chiloe and Concepcion, without the possible identity ever having occurred to me.

At last there was no resisting the conclusion.