May 19, 1870] 
NATURE 
47 
the River San Juan and its embouchure at Grey Town, offers a 
rare field for research to the naturalist and speculative geologist. 
In my early service—1834—I was engaged in the Admiralty 
nautical survey of the then harbour at the entrance of the River 
San Juan, subsequently well known as Grey Town. At that 
time it afforded a secure and fairly spacious anchorage for a few 
vessels of even 24ft. water (sheltered by a sandy peninsula) with 
a wide and clear approach. 
Between 1834 and 1839 the end of this sandy peninsula, 
Arenas Point, advanced considerably across the entrance towards 
the opposite shore, in a depth of five-and-a-half fathoms. In 
1859, the point had reached to within a cable’s length of the 
main land, or over 6000ft. in advance of its position twenty-five 
years previously, in depths varying from 33ft. to 18ft., practi- 
cally closing the port except to a small description of vessel. 
These great geological changes—if they may be ‘so called 
—in so short a period of time, destroying as they have done 
a useful port, are an interesting, and, so far as I know, an 
unique fact; but the point to which I would wish to refer in 
connection with the musical fish (?) is the vast amount of 
animal life observed at the time of the original survey alluded 
to. The port literally swarmed with fish, but we could not 
venture to haul the seine more than twice, from the circum- 
stance that large alligators came up in it, to the consternation 
of the fishermen and the destruction of the nets. Sharks of 
huge size rendered precaution from falling overboard a matter 
of some moment, as an unfortunate pet monkey discovered by 
being instantly seized. This abundance of life, proof of 
good feeding-ground, may have some connection with a well- 
developed species of musical fish; hut this speculation must 
be left for your naturalist readers. F. J. EVANS 
PERHAPS your correspondent, Charles Dennehy, M.R.C.S.L., 
R.M.S. Shannon, may find an interpretation of the nocturnal 
musical phenomenon (mentioned in NATURE, No. 28) experienced 
by iron ships when at anchor in seven or eight fathoms, with a 
bottom consisting of a heavy, dark sand and mud containing much 
vegetable matter, in the following natural system of gas-escape. In 
examining certain pools of water in the East, notorious for their 
poisonous qualities at certain seasons of the year, I was aware 
of intermittent risings of vast quantities of bubbles. The waters 
rested on vegetable deposits; if these were stirred up, large 
globules rose with considerable force, and I came to the conclu- 
sion that these air risings were due to the escape of gases from 
the decomposing vegetable matter. If any metallic body had 
met these bubbles as they rose, some sound would have been 
produced, the nature of it depending on various causes. The 
reason of the sound being heard on board ship between twelve 
and two, and not between two and four, is owing to a very 
simple, but beautiful rule of law: as the gases are at all times 
collecting, we might suppose that they would be at all times 
escaping, but as the surface of the bottom is of an elastic nature, 
the water pressure imprisons the gas as if it were within a valve ; 
but when the force of the gas overpowers the water pressure, 
there is a bubbling escape till the collected gases are expended, 
and thus I account for the sounds continuing ‘‘ about two hours, 
with but one or two yery short intervals.” It is by no means 
improbable that the musical performance occurs more than once 
in the twenty-four hours, though the ordinary noises of ship- 
board prevent its being audible. I believe there is no other 
way of accounting for this incident; but the test I would pro- 
pose is to stir up the bottom ona calm day with considerable 
force; if large quantities of air-bubbles arise, the sailors may rest 
satisfied that the concert is not given by ghost, mermaid, or 
siren, but simply by a continued contact of myriads of gas glo- 
bules against the ship’s bottom. The stirring up will not necessa- 
rily cause the sound, as the bubbles may be diverted by under- 
currents, H. P. MALEr 
The Sources of the Nile 
In the fifth (May) number of the Geographische Mittheilun- 
gen, I publish an article and two maps on “ Livingstone’s Travels 
and Discoveries from 1840 to May 1869,” one of the maps being 
carefully compiled from the original Portuguese publications of 
the Portuguese journeys since 1798—viz., those of Dr. Fr. José 
de Lacerda e Almeida, the Pombeiros Joao Baptista and Pedro, 
Major Monteiro, and others, showing all that is at present known 
of those regions. Both maps and text keep aloof from theories 
and speculations as to the connections of rivers and lakes dis- 
covered by Livingstone and the Portuguese with the Nile. 
a F 
Of the two points at issue, the one as to the connection of the 
Lake Tanganyika with Albert Nyanza, Livingstone says :— 
‘Tanganyika and Nyige Chowambe (Baker’s ?) are one water ;” 
but gives no proof of it, having evidently derived his information 
from hearsay. The mostreliable information on this point seems 
to me that supplied by Burton (Journal R. G. S., vol. 29, p. 
254) :—‘‘ At the head (northern end) of the Tanganyika lies the 
land of Uzige,” in which land, ‘‘according to the guides, six 
rivers fall into the Tanganyika in due order from the east—the 
Kuryamavenge, the Molongwe, the Kavinvira, the Kariba, the 
Kibaiba, and westernmost, the Rusizi or Lusizi. The latter is 
the main drain of the northern country, and the best authorities, 
that is tosay those nearest the spot, unanimously assert that it is 
an influent.” 
Regarding the Kassabi, the upper course of which was explored 
by Livingstone, Ladislaus Magyar, and Rodriguez Graga, it 
appears to me that the most reliable information we possess 
of its lower course is that supplied by Livingstone, as collected 
by him when at Cabango in 1855 (Livingstone’s Missionary 
Travels in South Africa, pp. 457 and 458):—‘‘ Several of the 
native traders here having visited the country of Luba, lying 
far to the north of this, and there being some visitors also from 
the town of Mai, which is situated far down the Kasai, I picked 
up some information respecting those distant parts. In going 
to the town of Mai, the traders crossed only two large rivers, the 
Laojima and Ohihombo. The Kasai flows a little to the east of 
the town of Mai, and near it there is a large waterfall. They 
describe the Kasai as being there of very great size, and that 
it thence bends round to the west. On asking an old man, 
who was about to return to Mai, to imagine himself stand- 
ing at his home, and point to the confluence of the Guango and 
Kasai, he immediately turned, and pointing to the westward, 
said, ‘ When we travel five days (thirty-five or forty miles) in 
that direction, we come to it.’ He stated also that the Kasai 
received another river, named the Lubilash, There is but 
one opinion among the Bovonda respecting the Kasai and 
Guango. They invariably describe the Kasai as receiving the 
Guango, and beyond the confluence assuming the name of Zairé 
or Zerézeré. And the Kasai, even previous to the junction, is 
much larger than the Guango, from the numerous branches it 
receives. Besides those we have already crossed, there is the 
Chihombo, at Cabango, and forty-two miles beyond this, east- 
ward, runs the Kasai itself; fourteen miles beyond that the 
Kaunguesi ; then, forty-two miles further east flows the Lolua ; 
besides numbers of little streams, all of which contribute to swell 
the Kasai. The town of Mai is pointed out as to the N.N.W. of 
Cabango, and thirty-two days or 224 miles distant, or about lat. 
S. 5° 45’. It is evident, from all the information I could collect 
both here and elsewhere, that the drainage of Londa falls to the 
north and then runs westward. The countries of Luba and Mai 
are evidently lower than this, and yet this is of no great altitude, 
probably not much more than 3,500 feet above the level of the 
sea. Having here received pretty certain information on a point 
in which I felt much interest, namely, that the Kasai is not navi- 
gable from the coast, owing to the large waterfall near the town 
OM Main se AuGuUSTUS PETERMANN 
Redaction der Mittheilungen aus 
Justus Perthes geographischer Anstalt, 
Gotha, May 2 
Scandinavian Skulls 
In his recent lecture on the ‘‘Forefathers of the English 
People,” Professor Huxley says, ‘‘It is a very remarkable cir- 
cumstance that the skulls of the existing Scandinavians . . . 
are Jong ;? and he contrasts their dolicephalous type with the 
round forms of South German, Swiss, and ancient Belgic heads, 
He also thinks it likely that the Scandinavian invasions of Eng- 
land brought a ‘“‘longer form of head ” into fashion amongst us. 
The same doctrine is taught by Sir Charles Lyell, in his 
“ Antiquity of Man,” and even in the sixth edition of his 
“Elements of Geology,” he says that the Scandinavian skulls of 
the dolmen period are brachycephalous, or round ; those of the 
iron age being dolicephalous, or long. 
Such notions were once current in Sweden and Denmark, but 
they are now exploded. Originally deductions from history, they 
rest on no basis of observed fact, and archzology plainly contra- 
dicts them. Thirty or forty years ago, Scandinavian savan‘s 
believed, on historical and philosophical grounds, that Lapps and 
Finns were the earliest inhabitants of the Baltic North, that after 
