“Yesterday was one of the happiest days of my life, and I want to share it with you. Here I am at Tijuca, a cluster of hills, about eighteen hundred feet high and some seven or eight miles from Rio, in a charming cottage-like hotel, from the terrace of which you see a drift hill with innumerable erratic boulders, as characteristic as any I have ever seen in New England. I had before seen sundry unmistakable traces of drift, but there was everywhere connected with the drift itself such an amount of decomposed rocks of various kinds, that, though I could see the drift and distinguish it from the decomposed primary rocks in place, on account of my familiarity with that kind of deposits, yet I could probably never have satisfied anybody else that there is here an equivalent of the Northern drift, had I not found yesterday, near Bennett’s hotel at Tijuca, the most palpable superposition of drift and decomposed rocks, with a distinct line of demarcation between the two, of which I shall secure a good photograph. This locality afforded me at once an opportunity of contrasting the decomposed rocks which form a characteristic feature of the whole country (as far as I have yet seen it) with the superincumbent drift, and of making myself familiar with the peculiarities of both deposits; so that I trust I shall be able hereafter to distinguish both, whether they are in contact with one another or found separately. These decomposed rocks are quite a new feature to me in the structure of the country. Imagine granite, gneiss, mica slate, clay slate, and in fact all the various kinds of rocks usually found in old metamorphic formations, reduced to the condition of a soft paste, exhibiting all the mineralogical elements of the rocks, as they may have been before they were decomposed, but now completely disintegrated and resting side by side, as if they had been accumulated artificially in the manner you have seen glass cylinders filled with variously colored sands or clays to imitate the appearance of the beds of Gay-Head. And through this loose mass there run, here and there, larger or smaller dikes of quartz-rock or of granite or other rocks equally disintegrated; but they retain the arrangement of their materials, showing them to be disintegrated dikes in large disintegrated masses of rock; the whole passing unmistakably to rocks of the same kind in which the decomposition or disintegration is only partial, or no trace of it visible, and the whole mass exhibiting then the appearance of an ordinary metamorphic set of rocks.