404 A JOURNEY IN BRAZIL. 
de Janeiro to the top of the Serra do Mar, where, just out- 
side the pretty town of Petropolis, the river Piabanha may 
be seen flowing between banks of drift, in which it has ex- 
cavated its bed ; thence I have traced it along the beautiful 
macadamized road leading to Juiz de Fora in the province 
of Minas Geraes, and beyond this to the farther side of the 
Serra da Babylonia. Throughout this whole tract of country 
the drift may be seen along the roadside, in immediate 
contact with the native crystalline rock. The fertility of 
the land, also, is a guide to the presence of drift. Wherever 
it lies thickest over the surface, there are the most flourish- 
ing coffee-plantations ; and I believe that a more systematic 
regard to this fact would have a most beneficial influence 
upon the agricultural interests of the country. No doubt 
the fertility arises from the great variety of chemical ele- 
ments 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 con- 
firmed by the reports of some of my assistants, who have 
been travelling in other parts of the country. Mr. Fred- 
erick 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 every- 
where 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 in- 
terior, has visited, with the same objects in view, the 
valleys of the Rio San Francisco and the Rio das Yelhas, 
