REVIEWS. 119 



The tributary streams, watering this vast territory, are numerous, and 

 present to the naturalist some very remarkable differences in the character 

 of the vegetation on their banks, the animals that inhabit them, and even 

 the very colour of their water. This last point of difference is so remarkable 

 as to enable them to be classed in three great groups — the white-water 

 rivers, the blue-water rivers, and the black-water rivers. To the first of 

 these divisions the main stream of the Amazon itself belongs ; and it would 

 appear that its colour (a pale yellowish olive) is not entirely dependent on 

 free, earthy matter, but rather on some colouring material, held in solution. 

 All the rivers that rise in the mountains of Brazil belong to the blue or 

 clear water class ; of these the principal are the Tocatiiis, the Xingu, and 

 the Tapajoz. Above the Madeira the black-water rivers are first met with. 

 Of these the Rio Negro is the most celebrated ; it rises in 2° 30' N. lat., 

 where its waters are much blacker than in the lower part of its course. 

 The peculiar colour of these rivers would appear to be produced by the 

 solution of decaying leaves, roots, and other vegetable matter. 



The examination of the geological peculiarities of so vast an area, and 

 the comparative rarity of natural sections falling under the observations of 

 a single individual, is of but little value. It is, however, remarkable that Mr. 

 "Wallace was unable to find any trace of fossil remains, which prevents any 

 geological age being assigned to the various beds of rock which occur. To 

 the botanist, however, the riches of this district are most attractive. Mr. 

 Wallace thus speaks of the vegetation : — 



" Perhaps no country in the world contains such an amount of vegetable matter 

 on its surface as the valley of the Amazon. Its entire extent, with the exception 

 of some very small portions, is covered with one dense and lofty primeval forest — 

 the most extensive and unbroken which exists upon the earth. It is the great 

 feature of the country — that which at once stamps it as a unique and peculiar 

 region. It is not here, as on the coasts of southern Brazil or on the shores of the 

 Pacific, where a few days' journey suffices to carry us beyond the forest district 

 and into the parched plains and rocky serras of the interior. Here we may travel, 

 for weeks and months inland, in any direction, and find scarcely an acre of ground 

 unoccupied by trees. It is far up in the interior, where the great mass of this 

 mighty forest is found ; not on the lower part of the river, near the coast, as is 

 generally supposed. 



u A line from the mouth of the river Parnaiba, in long. 41° 30' W., drawn due 

 west towards Guayaquil, will cut the boundary of the great forest in long. 78° 30', 

 and for the whole distance, of about 2,600 miles, will have passed through the 

 centre of it, dividing it into two nearly equal portions. 



" For the first thousand miles, or as far as long. 56° W., the width of the forest, 

 from north to south, is about 400 miles ; it then stretches out both to the north and 

 south, so that in long. 67 °W. it extends from 7° N., on the banks of the Orinooko, 

 to 18 oS., on the northern slope of the Andes of Bolivia, a distance of more than 

 seventeen hundred miles. From a point about sixty miles south-east of Tabatinga, 

 a circle may be drawn of 1,100 miles in diameter, the whole area of which will be 

 virgin forest." 



Forests our author regards as the characteristic of the New World, as 



