a most beneficial influence
upon the agricultural interests of the country. No doubt the fertility
arises from the great variety of chemical elements contained in the
drift, and the kneading process it has undergone beneath the gigantic
ice-plough,--a process which makes glacial drift everywhere the most
fertile soil. Since my return from the Amazons, my impression as to the
general distribution of these phenomena has been confirmed by the
reports of some of my assistants, who have been travelling in other
parts of the country. Mr. Frederick C. Hartt, accompanied by Mr.
Copeland, one of the volunteer aids of the expedition, has been making
collections and geological observations in the province of Spiritu
Santo, in the valley of the Rio Doce, and afterwards in the valley of
the Mucury. He informs me that he has found everywhere the same sheet
of red, unstratified clay, with pebbles and occasional boulders,
overlying the rock in place. Mr. Orestes St. John, who, taking the road
through the interior, has visited, with the same objects in view, the
valleys of the Rio San Francisco and the Rio das Velhas, and also the
valley of Piauhy, gives the same account, with the exception that he
found no erratic boulders in these more northern regions. The rarity of
erratic boulders, not only in the deposits of the Amazons proper, but in
those of the whole region which may be considered as the Amazonian
basin, is accounted for, as we shall see hereafter, by the mode of their
formation. The observations of Mr. Hartt and Mr. St. John are the more
valuable, because I had employed them both, on our first arrival in Rio,
in making geological surveys of different sections on the Dom Pedro
Railroad, so that they had a great familiarity with those formations
before starting on their separate journeys. Recently, Mr. St. John and
myself having met at Para on returning from our respective journeys, I
have had an opportunity of comparing on the spot his geological sections
from the valley of the Piauhy with the Amazonian deposits. There can be
no doubt of the absolute identity of the formations in these valleys.

Having arranged the work of my assistants, and sent several of them to
collect and make geological examinations in other directions, I myself,
with the rest of my companions, proceeded up the coast to Para. I was
surprised to find at every step of my progress the same geological
phenomena which had met me at Rio. As the steamer stops fo