’ 
NATURE ~ 
~ 
(Feb. 22, 1883 
1 
having the shape and size of an orange, but resembling 
internally the American muruenia, that produces purgative 
effects when taken in large doses; the ¢omgo, similar in 
form and dimensions to the white plum ; and the ¢uzda, 
almost equal to a cherry in taste, and having black seeds. 
The abundance of wax is really remarkable, and towards 
the south and south-east it constitutes an important 
branch of industry.” 
At this point the two travellers separated in order to 
proceed northwards on different sides of the Cuango, and 
met again at Cassange, where they fell in with Dr. Max 
Buchner, on his way to the great Muata Yanvo. Of this 
famous potentate Messrs. Capello and Ivens give a fancy 
portrait, which contrasts markedly with that taken from 
the original by the German explorers who have recently 
done so much for a scientific knowledge of the region 
through which the route of the Portuguese travellers lay. 
Cassange may be regarded as the furthest Portuguese 
outpost, and a busy centre it is. 
Yacca, the furthest limit of the expedition, was reached 
in May, 1879, and although innumerable small lakes and 
many streams had been passed, the region beyond was 
found to be an arid desert, brooded over by “the silence 
of the grave.” Here is a summary of the travellers’ 
observations on the course of the Cuango from its source 
to the limit of their journey, about 140 miles from where 
the river discharges into the Congo :— 
“From parallel 11° 30’, approximately, where its 
sources are to be found, up to 5° 05’ at the Quicunji 
cascade, the river has a sinuous course of 580 geographic 
miles, and a total fall between its extreme points of 
about 3 feet 4 inches per mile. Rocks, stones, rapids, 
and cataracts interrupt the stream, and twelve of the 
points at which they do so are known to us, namely, the 
first at parallel 10° 17’, to the east of Muene-songo; the 
second at 10° 25’, near the Camba rivulet ; the third at 
10° 08’, Caxita rocks; the fourth at 10° 05’, the Louisa 
falls; the fifth at 10° 05',a cataract a little above Port 
Muhungo ; the sixth at 9° 20’, Zamba; the seventh at 
19° 19’, Tuaza ; the eighth at 9°, cataract Cunga-ria- 
Cunga ; the ninth at 7° 42’, Suco-ia-Muquita or Suco-ia- 
n’bundi ; the tenth at 7° 38’, just below the Camba; the 
eleventh at 7° 35’, in the midst of numerous islands; and 
the twelfth at 5° 05’, the Quicunji waterfall, which is only 
passable after the heavy rains. The greatest navigable 
tract, therefore, is that space which lies between the 
cataract at 7° 35’ and Quicunji, or about 190 geographic 
miles. The river there is of variable width, never less than 
76% yards, and from 5 to 20 feet in depth. The current 
loses a little of its speed in the upper section, where the 
stream in the summer season has a fall of about 3 feet 
2 inches per mile. We think it well to mention that our 
longitudes being strictly correct, as the record, partly 
chronometric, was compared both on departure and 
arrival at the Portuguese station of Duque de Braganca, 
and the latter again at the terminus on the coast, it ap- 
pears to us that the point of affluence of the Cuango (or 
Ibari-N’Kutu) as marked upon the maps, just above 
Stanley Pool, is erroneously placed considerably to the 
eastward.” 
Major von Mechow, who has been exploring the river 
urther down its course, has found it equally unnavigable, 
and we may say that the maps illustrating Mr. Stanley’s 
last journey to the Congo place the mouth of the river | 
further west than on those of his famous trans-African | 
expedition. It was this river which Mr. Stanley as- | 
cended in his little steamer, and found it expanding 
into a broad lake. Messrs. Capello and Ivens came to | 
the conclusion, confirmed by Major von Mechow, that | 
no such lake as Aquilonda exists in this quarter. ‘The 
travellers returned by a somewhat different route, staying 
for some time at Pungo N’Dongo, with its famous rocks, 
and reaching Loanda in October, 1879. 
The work abounds with illustrations of the country and 
the people, many of them devoted to natural history. On 
the animal and plant life of the district traversed there 
are many valuable notes, and in the appendix will be 
founc, besides tables of geographical observations and 
heights above sea-level, lists of additions to the fauna and 
flora, tables of African dialects, and a N’Bunda Vocabu- 
lary. There is a good summary of the general results 
in the concluding chapter, in which the authors have the 
following observations on the geology of the continent :— 
“The physical configuration of the African continent, 
and more especially of the portion south of the equator, 
is nowadays too well known to require minute descrip- 
tion. It may be summed up in these few words: a 
depressed central basin surrounded by a vast circle of 
high land, gradually descending to the sea, and rent by 
deep ravines, through which rush huge watercourses, 
engendered in the interior, till they overflow and seek the 
lower level fronting the ocean. From a very general 
geological point of view we may define the regions run- 
ning from the littoral to the interior in the following 
order, viz. limestone, sandstone, and granite. But on 
going more minutely into the subject we shall find that 
these distinctions are not very exact; inasmuch as the 
component parts frequently run into each other and 
change places, while precise lines of demarcation are 
wanting. The geological formation on the western coast 
at the points observed by us between Loanda and Mossa- 
medes, and even further to the north, exhibits generally 
near the sea a belt of tertiary deposits, with abundant 
masses of sulphate of lime and sandstone, from which 
they are separated by beds of white chalk alternating 
with primary rocks, for the most part gneiss, abounding 
in quartz, mica, hornblende, granite, and granulated 
porphyry. Towards the south large tracts of feldspar 
become visible. At Mossamedes whole mountains are 
composed of sulphate of lime ; while carbonate of lime, 
accumulated in shells, is very frequent. Both rock-salt 
and nitrate of potash are found in stratification. Along 
the Mocambe chain, we were informed, there exists a 
basaltic line of great length. From that point the shift- 
ing soil may be said to commence, extremely abundant in 
sand, constituting true sa/aras, as in the parallel of Tiger 
Bay. In the transition from the lower zone towards the 
interior, for instance at Dondo, vast tracts of schist rock, 
in perfect laminae, compose the soil; and sandstone, 
reddened by oxide of iron, is visible in every direction. 
Proceeding further into the interior we find, in a perfectly 
mountainous region, the ground to be composed of 
granite-quartzy rock, extremely hard and compact; this 
is the case throughout the belt crossed on the way and 
up to Pungo N’Dongo, the surface soil being formed by 
the disintegration of the granite itself. These geological 
characteristics will naturally be repeated to the south and 
north in identical parallel regions, with variations in the 
high table-land, where we meet occasionally with hard 
and tough red sandstone and rocks of feldspar as in the 
basin of the Lucalla.” 
In the same chapter will be found abundant notes on 
the various tribes visited, which, although the authors’ 
ethnology appears to us by no means sound, are still a 
valuable contribution to a knowledge of the African 
peoples. As evidence of the important contributions to 
the natural history of West Africa, we give a few of the 
illustrations bearing on the subject. 
ON THE AURORA BOREALIS* 
HAVING been requested by this journal to give an 
account of my latest researches into the nature of 
the aurora borealis, I must explain that my lateness in 
t In reference to the present interesting communication from Herr Sophus 
Tromholt, from his station in Ultima Thule, we ought to point out that Herr 
Tromholt was, at the time of writing, not aware of the important discovery 
as regards the nature of the aurora made by Prof. Lemstrém at the Finnish 
station of Sodankyla during December last, and of which an account 
appeared in Nature, vol. xxvii. p. 
322 
