322 



THE FARMER'S MAGAZINE. 



principal tributaries. The six samples put into my 

 hand represented the compost or ooze of the shores of 

 the Rio Madeira, the Rio Topajo, the Rio Trombetto, 

 the Rio Cupari, and the Rio Negro, whose waters unit- 

 ing themselves to those of the Casiquiare, establish the 

 junction of the two greatest rivers of the New World, 

 the Oronoco and the Amazons ; a communication so 

 astonishing that geographers have doubted its reality 

 until the memorable exploration of Alexander voa Hum- 

 boldt. 



The Earth from the shores of the Bio Madeira. — 

 Argillaceous ; very plastic ; bluish grey, enclosing 

 debris of radicles ; does not effervesce with acids ; 

 forests; culture, tobacco and sugar-caue. 



The Earth taken at the embouchure of the Rio 

 Trombetto in the .I'lwaron*.— Very argillaceous ; a clear 

 brown; makes no effervescence ; forests; culture, tro- 

 pical. 



The Earth taken from, the embouchure of the Rio 

 Negro in the Amazons. — Furnished by a yellow sand, 

 very loose; alluvium, having its origin in the granitic 

 mountains of Guiana; does not effervesce; a steppe 

 clothed with herbaceous vegetation. 



The Earth taken from the shores of Lake Saracca, 

 near the Amazon. — Mixture of clay and sand ; a deep 

 brown, interspersed with debris of roots ; makes no 

 effervescence. The deposit forms on the shore a cliff of 

 from 80 to 100 metres thickness. The sample has been 

 taken from land cultivated with tropical plants. 



The Earth from the plateau of Santarem, elevated 

 from 200 to 300 metres above the Amazons. — Mixture 

 of sand and clay, almost black ; abundant debris of 

 vegetable matter, having sometimes the appearance of 

 fossil wood ; makes no effervescence ; soil very fertile ; 

 rich culture of cocoa trees. 



The Earth taken from the shores of the Rio Cupari, 

 at the point of junction with the Rio Tojjajo, is the 

 most remarkable for its constitution and extraordinary 

 fertility. It forms a bank, one or two metres thick, 

 arising from the superposition of alternate strata of sand 

 and leaves, often well preserved, of a deep brown. It 

 becomes entirely disintegrated, and then the sand is 

 easily separated by the sieve. From 100 parts we 

 took — 



Sand 60 



Decayed leares . . . . . . 40 



100 



The soil of Cupari must be considered as a deposit of 

 compost of leaves, the extent and power of which ex- 

 plains at once both the vigorous vegetation and the for- 

 midable insalubrity of that hot and humid locality. 

 This natural compost exhibits the peculiarity of con- 

 taining no trace of nitrates, whilst it is unusually rich in 

 ammonia. 



I have disposed the results of these experiments in a 



tabular form. In discussing them we cannot refrain 

 from offering this observation — that the soils of Brazil, 

 undoubtedly the most fertile we are acquainted with, are 

 derived from Feldspathic rocks, and contain only a few 

 thousandth parts of lime. 



In a kilogramme of air-dried earth — 



Rio-Madeira 



Rio-Trombetto 



Rio-Negro 



Amozona, near Lake T 



Saracca / 



Amazoua-Santarem.. .. 

 Rio-Cupari (natural "I 



compost) J 



Azote enter- 

 ing into the 

 composition 

 of organic 

 matters. 



Gtamm. 



1.428 

 1.191 

 0.688 



1.820 



6.490 



6.850 



Ammonia 



well 



formed. 



Gramm. 



0.090 

 0.030 

 0.038 



0.042 



0.083 



0.525 



Nitrate 

 equivalent 



to 

 nitrate of 



potash. 



Gramm. 



0.004 

 0.001 

 0.001 



0.000 



0.011 



0.000 



Rio-Madeira 



Rio-Trombctto 



Rio-Negro 



Amazons, near Lake 1 



Saracca J 



Amazons-Santarem .... 

 Rio-Cupari (natural 1 



compost) J 



Phosphoric 

 acid. 



Gramm. 



0.864 



0.792 

 0.176 

 0.288 

 0.445 



It appears from these researches that, in spite of 

 origins, diversity of situations, on the borders of the 

 Rhine, and in the valley of the Amazons — in soils super- 

 abundantly improved by European cultivation, and in 

 alluviums deposited by the great rivers of the impene- 

 trable forests of America — the vegetable earth contains 

 always the same fertilizing principles, the same that we 

 find in larger doses in compost, the spoils of what has 

 vegetated and lived on the globe ; ammonia, or nitric 

 acid, the most ordinary of ammoniacal salts united to 

 nitrates ; phosphates mixed with alkaline and earthy 

 salts ; and constantly organic azotous matters, of which 

 the carbon, given by analysis, is evidently the index, and 

 in some sort the measure. Complex matters incom- 

 pletely studied, to which, in the mean time, according 

 to my experiments I recognize that singular property of 

 producing, under certain influences acting in the normal 

 conditions of arable land, nitric acid and ammonia, that 

 is to say, the two combinations in which azote is assi- 

 milable by plants. Boussingault, 



(Member of the Academy of Science, and of 



the Imperial and Central Society 



of Agriculture.) 



