Wallace Letters Online

Share this:

Record number: WCP3673

Sent by:
Alfred Russel Wallace
Sent to:
[not recorded]

Sent by Alfred Russel Wallace, [address not recorded] to [addressee not recorded] [address not recorded] on  1853.

Record created:
11 January 2012 by Catchpole, Caroline
Verified by:
22/08/2012 - Catchpole, Caroline (All except summary checked);


No summary available at this time.

Record contains:

  • enclosure (1)

View item:

ENCLOSURE (WCP3673.3576)

An enclosure handwritten by in English.

Manuscript "On the Rio Negro" written by Alfred Russel Wallace. Beneath the title is written in Wallace's hand "communicated by Mr. Petermann. Read 13 June 1853".

Held by:
Royal Geographical Society
Finding number:
JMS 6/53
Copyright owner:
ŠA. R. Wallace Literary Estate
Record scrutiny:
22/08/2012 - Catchpole, Caroline;

Physical description

Transcription information




On the Rio Negro, by Mr Alfred R. Wallace

Communicated by Mr Petermann. Read June 13 -- 1853.

The Rio Negro or "Black river" is one of the largest northern tributaries of the Amazon. It enters that river at about 9800 miles from its mouth, the Ocean, and at a distance of 880 miles up, while near its source it communicates, by means of the Cassiquiare, with the Orinocko.

It joins the Amazon in a line with the course of that river and does not come at right angles like most a tributaryies, so that it would appear at first sight to be the true continuation of that it river, but the smaller volume of its waters the general direction of its course and the position of its sources all show that it is but an affluence of that great River.

The most striking characteristic of the Rio Negro is that from which it derives its name, its black waters. And this is no imaginarytive or fanciful appellation, for as much as the waters of the ocean are blue, so are those of this river jet black. The sudden change from the pale yellowish olive of the Amazon is most striking, and must have immediately suggested its name to its first European discoverers. The water when examined in a glass vessel is seen to be very slightly tinged with a clear coffee brown, and where it runs over white sand at the depth of a few feet, it appears of a rich golden brown colour. In deep water it appears is - (in every variety of light) -- jet black.


720 mouth of Rio Negro to Mouth of Uaupes

380 Uaupes to Mucura[?]


800 miles Amazon to Barra

[[3]]2 The colour varies in intensity in different parts of its course. In the lower part there is slight impurity of colour olive tint, as caused by a mixture of sediment; higher up in the rocky district it is much purer and more transparent, and towards its sources above the falls and in its smaller branches it the water attains its maximum of purity and colour. The tributary streams vary much in colour this particular. All the small streams on its southern side above those which communicate with the Solimoȇs, are black, the greater river Uaupés alone being of a rather paler colour though it too, is a black water river. On the north however side also there are some black water streams while though the greater proportion number are white. The small streams before we come to below the Rio Branco are black. That stream river however is white to a remarkable degree, its waters being actually milky in appearance. Above it, the Uaracá and some other small streams are black, while the Padauarí, Daraha Maravihá & Cababurís are white water rivers, though none of them so much so as the Rio Branco, or even as the Amazons. Other small streams flowing between them have black water. [These various coloured waters may we believe readily be explained accounted for by the nature of the country the stream flows through. The fact that the most purely black [[4]]3 water rivers flow through districts of dense forest, & have granite beds, seems to shew that it is the percolation of the water through decaying vegetable matter which gives it its peculiar colour. Should the stream however flow through any extent of alluvial country, or through any districts [word deleted] where it can gather much light coloured sedimentary matter, it will change its aspect and we shall have the phenomenon of alternating white and black water rivers. The Rio Branco & most of its tributaries rise in an open rocky country & the water in the upper there parts course is pure & uncoloured; it must therefore be in the lower part of its course that it obtains the sediment that gives it so remarkably a light colour, and it is remarkable worthy of note, that all the other white water tributaries of the Rio Negro have a course run parallel to the Rio Branco, and therefore probably obtain their sediment from a continuation of the same deposits; only as they flow entirely through a forest district producing brown water, & probably had their waters already tinged, the result is not such a strikingly light tint as in the case of that River. [[5]]4 The Isánna, Xié, and Guaniá or Upper Rio Negro itself, which all have remarkably black waters, we know flow entirely through a dense forest and granitic district, and none of them extend west of the much beyond the parallel of 72° W. of Greenwich. The Guaviare & the Japurá which rises considerably W[est] of this line have white waters, & the Uaupés which also rises near them & much further West than all the other tributaries of the R[io] Negro, has also paler waters, & in its upper course nearly white.

On entering ascending the Rio Negro, at about ten miles from its mouth we reach the city of Manao, or Barra do Rio Negro, the capital of the new province of Amazonas. At 340 miles the River divides into two branches, and from this point to the mouth of the Rio Branco at about 200 miles up, the N[orth] bank is never to be seen from the south side, up which all the traffic takes place. The River is here more like an immense lake or labyrinth of Islands, and is, from the best information I can obtain from ten to fifteen or perhaps twenty miles wide. For about 70 miles below the village of Ayrão, there are high banks of clay & gravel & sandstone -- below and [[6]]5 above this are tracts of low flooded lands, & between Ayrão and the next village, f Pedreiro, are two rivers channels which communicate with the Solimões, or upper Amazon. Below Ayrão commences a hard sandstone rock; about Pedreiro, it is becomes highly crystallizedine, & just above a little further opposite the Rio Branco, is it changes into a true Granitic rock, which however immediately ceases, & does not again appear untill[sic] we arrive at the commencement of the great granitic district of the Upper Rio Negro. Immediately on passing the Rio Branco, Islands again appear & the opposite bank is not ever seen visible for 240 miles further, when in about 64.20 W[est] the river is clear & its width,[letters deleted] determined by triangulation from a measured base, is 4 1/4 miles. In this space we have passed the towns of Carvoéiro, Barcéllos, Cabuquéno, and Bararuá, all which are all of them small, half ruined, & almost uninhabited villages. About Carvoeiro is a labyrinth of lakes and Islands in which even experienced Pilots are sometimes lost. From the river Qúiuiní to Xibarú are high banks of clay & earth, of various colours, with occasional inlets, lakes, & tracts of flooded lands.

[[7]]6 All the islands as well as the low parts of the River banks, are flooded annually for several months, generally from April to August or September -- the rise of the river being from 30 to 50 feet.

In 64.° 25. W[est] Longitude, The Granitic formation commences & extends without interruption up to the sources of the River & of all its tributaries. and From here up, this point there is less flooded land on the banks, & some Islands are always above water. Islands still continue in great abundance up to Castanheiro. From thence to the Cataracts of S[ao] Gabriel they are more rocky & smaller. The river here averages 3 or 4 miles wide & up towards the falls 1 mile.

About A little below Castanheiro begin the isolated granite peaks which are thence plentiful all over up the River. The Serra de Jacamí is the first of any size, a group of isolated conical granite hills of 500 or 600 feet high. About twenty miles below S[ao] Gabriel are the Serras de Curicuriarí, which must be nearly 3000 feet high & all are the most lofty in the whole district, though the Serras de Cababurís, near the sources of the river Cababurís are perhaps nearly equal to them.

[[8]]7 The Cataracts of the Rio Negro extend in length about 20 miles and are a series of rapids where the river flows among Islands and vast masses of granite rock, forming Cataracts falls, eddies and rapids, which greatly obstruct navigation. They may be descended in a few hours with a skilful pilot but a laden canoe often takes a week to ascend them, & at some seasons more, & then with great peril both to life & property.

Above the falls the River keeps an average width of about the 3/4 mile to S[an] Carlos, the first town in the Republic of Venezuela. Above the Cassiquiare it is called the Rio Negro takes the name of the Guainiá & gets shallower & so narrower and more shallow, varying from 1/4 to ½ a mile wide up to Maróa, the last village on the River. Above this it winds about, turning to the West & has its sources certainly to the Eastward of the parallel meridian of 71° [letter crossed out] W[est] Longitude, and probably near that of 70°.

The Uaupés is the largest tributary of the Rio Negro above the falls, & is perhaps larger than thate Rio Negro itself; & by some is supposed to be the principal stream.

[[9]]8 We ascend it for about 130 miles in smooth water, when we come to the first group of cataracts just above the village of St. Jeronymo. There are three falls, & they are much more furious and dangerous than those of the Rio Negro, the River being confined into a very narrow channel, & in the wet season rushing down with incredible fury.

Up to this point the river Uaupés is generally more than a mile wide. Above these falls we have about 50 miles more of smooth water, when with the next fall begins a series of cataracts extending for 180 miles further up the River. They are placed in four principal groups, and there are 50 of them which have native names. Some of these are mere rapids, others foaming cataracts & others again real falls of ten or fifteen feet perpendicular height. Above these the River is quite unknown. One more great fall the "Jurupari Caxoeira" exists, at least 100 miles further up, & above this again, traders have ascended for 12 ~ 15 days, & report a great river with little current


The mean temperature of the water of the Rio Negro in its lower part in the month of September, was at 6 a.m. 85.°4, at 2 pm. 86.°5 and at 6 pm. 86°.4, giving very nearly 86° as the mean temperature for the month, which is nearly one of the hottest in the year. The mean temperature of the air for the same period was at 6 am. 76°, and at 2 pm. 92°.5. It is probable that at no time f would the temperature of the water in the lower part of the Rio Negro be less than 80°.

[[11]]10 with whiter water, & with trees[,] birds & fishes which assimilate it to the Upper Amazon.

The rise of country in the valley of the Rio Negro is remarkably slight. Humboldt gives the height of S[an] Carlos as 812 feet above the sea, but I have reason to believe it is much less. than this.

Observations of the boiling point of water made at the mouth of the Rio Negro and at different points up to near S[an] Carlos, gave me a rise of about 300 feet. The height of the mouth of the Rio Negro cannot be more than 200 feet and probably not more than 150 judging from the height of Tabatinga a thousand miles higher up the River given by Martins as 620 feet & from the fact of the influence of the tides being felt at Obydos, more than half way from the Ocean to the mouth of the Rio Negro. We should therefore have 400 to 500 feet for the height of S[an] Carlos, which I cannot but think is not far from the truth. It is to be observed that Humboldt mentions air having got into his barometer tube, which rendered refilling necessary & of course destroyed the trustworthiness of the instrument.

It is a remarkable fact that the pressure of the atmosphere at the mouth of the Rio Negro as observed by from the boiling-point of water & by an aneroid in the possession [[12]]11 of my friend Mr. Spruce seems to be was greater than at Pará at the level of the sea, giving it a negative result for the altitude. It therefore seems probable that there is a difference of atmospheric pressure in the interior of S[outh] America independent of altitude.

Having unfortunately broken my thermometers I had no means of ascertaining the height I reached on the Uaupés, but from an estimate of the height depth of the falls I do not think the my farthest point I visited could be more than 1000 feet above the sea level.

The whole of the country through which the Rio Negro and Uaupés flow, is one unbroken forest, which also extends over every one of the countless islands whyich are found in every part of its [letters deleted] course. The numerous villages marked on maps fo whose names are marked on our maps, are little groups of mud-walled, palm-thatched cottages, and it seldom happens that more than two or three in a village are inhabited, the Indians preferring to reside in their houses secluded in the forest, up the various narrow streams that everywhere abound. [The articles of export of the country are chiefly salsaparilha & piassaba. The latter is the article material used to make the brooms now used for sweeping our streets, and is the produce of a palm found only on [[13]]12 on[sic] some of the tributaries of the Rio Negro. /

The inhabitants of the banks of the main stream of the River are semicivilized, and are nominal Christians; but the most of the tributary streams & especially the Uaupés, are inhabited by numerous various tribes of uncivilized & unchristianized Indians.

The map which I have constructed of the Rio Negro and the Uaupés, is from observations made during two ascents and descents of those Rivers in the years 1850, 1851, and 1852. The only instruments I possessed were a prismatic compass, and a pocket sextant. and a watch. With the former I took bearings of every point & island visible on my voyage, with sketches embodying all the information I could obtain from the persons, well acquainted with the river, who accompanied me; and I constantly determined the variation of the needle, which was from 4 ¾ to 5° East. With the sextant I was enabled to determine ascertain obtain a few latitudes. with tolerable accuracy. The position of Barra on the Rio Negro I have taken from Lieut. Smith, who determined it on his descent of the Amazon in the year 1835. The other extreme point, S[an] Carlos & the mouth of the Cassiqquiare, I have taken from Humboldt and Schomburgh. For my positions [[14]]13 between these points I have had to trust to the time occupied in the passage to the different points various stations, which I always accurately noted, both in my ascents and descents, and thus obtained a mean which I think will not be very far from the truth.

I also thus obtained gained experience as to f the rate of travelling in canoes under different circumstances, which I have had to depend upon in determining my distances on the Uaupés, where I had no other means method of ascertaining the longitude of the extreme point reached.

The map therefore does not pretend to any minute accuracy in general positions, but only to give an idea of the physical features of a River yet still very imperfectly known.

The following are the most important distances on the Rio Negro:

From its mouth to the falls of São Gabriel -------------------------- 710 miles.

[From its mouth] to the entrance of the Cassiquiare --------------- 900 miles.

[From its mouth] to its supposed source in Long[itude] 70 W[est] 1200 miles.


1. The word Read appears at the foot of the page but is not part of the text.

2. This page is numbered 2 in the manuscript.

3. This page is numbered 3 in the manuscript.

4. This page is numbered 4 in the manuscript.

5. This page is numbered 5 in the manuscript.

6. This page is numbered 6 in the manuscript.

7. This page is numbered 7 in the manuscript.

8. This page is numbered 8 in the manuscript.

9. This page is not numbered.

10. This page is numbered 9 in the manuscript.

11. This page is numbered 10 in the manuscript.

12. This page is numbered 11 in the manuscript.

13. This page is numbered 12 in the manuscript.

Please note that work on this transcript is not yet complete. Users are advised to study electronic image(s) of this document, if available.