162 
PHYSICAL HISTORY OF THE 
Throughout this whole tract of country, in the 
greater part of which travelling is easy and 
delightful, — an admirable line of diligences, 
over one of the finest roads in the world, being 
established as far as Juiz de Fora, — 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 flourishing 
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 fertil¬ 
ity arises from the great variety of chemical 
elements contained in the drift, and the knead¬ 
ing 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 im¬ 
pression 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. Cope¬ 
land, one of the volunteer aids of the expedi- 
