\ 
_ tothe Geological Magazine in July 1872, but it was not so fortu- 
nate as to meet with acceptance from the editor. The following 
extracts coincide singularly with the opinions of Prof. Stanley 
evons :— 
The river Rauma, at the western end, which gives its name 
to Romsdal, is the za¢ural outlet. The outlet to the river Logen, 
at the eastern end, is entirely avdificia’, The water-parting there, 
between Romsdal and the Dovre Feld, is an ancient ridge of 
drift.” A cut has been made by man this ridge. The 
stream through this cut now works a saw mill, but was for- 
merly connected with the old iron works, The one outlet 
from the lake enters the mill pool, from which there are 
two outlets, one to serve the mill the other for the waste 
water. All these three outlets are kept each at its required level 
artificially, that is, with piles, logs, boulders, and rubble, so that 
the quantity of water which is let out of the lake is regulated by 
‘the miller and his men.’ The case is precisely equivalent to 
the Black Loch, in Dumfriesshire, whose zafura/ (!) outlet is an 
iron sluice in a stone dam opening to a mill lead cut through the 
water-parting to Lord Bute’s mill. (See Atheneum, Aug. 6, 
1864, and 25 in. Ordnance maps.) If such lakes as these are lakes 
with two outlets, then the new conduit for the water supply of 
Glasgow makes Loch Katrine a Jake with two outlets. An old 
dry channel is in direct continuation of the present milllead. It 
so close to the old iron work as actually to touch its 
int If, as I imagine (as does also Prof. Stanley Jevons), the 
two are connected with each other in origin, the artificial outlet 
to the lake may be of very great antiquity. 
A notice in NaTuRE, of a new work by Capt. Burton (1872), 
quotes these words of his: ‘‘The northern and north-western 
portions of the so-called ‘Victoria Nyanza’ must be divided into 
three independent broads or lakes . . . in order to account for 
the three effluents, within a little more than sixty miles.” Here, 
then, the great traveller adopts my dictum, that “a lake can 
only have one outlet.” I first published this dictum in the 
Atheneum, July 4, 1863, when the late lamented Capt. Speke, 
in his “Sketch Map,” gave four outlets to Lake Victoria Ny- 
anza, three on ‘‘native information ;” and in the Atheneum, 
July 25, Isaid, ‘‘I think that the native information will prove 
to be erroneous.” GEORGE GREENWOOD 
Brookwood Park, Alresford, Aug. 15 
As Prof. Jevons has revived the question of the existence of 
lakes possessing more than one outlet, I would invite the at- 
tention of your readers to what appears to me an unequivocal 
instance of the kind, though on a small scale, in the neighbour- 
hood of the place whence I write. 
On the high and very broken ground between the old moun- 
tain road from Dolgelly to Towyn (which runs at the foot of 
Cader Idris) and the south shore of the estuary of the Mawd- 
dach is a watershed, which separates streams flowing directly into 
the estuary by Capel Arthog from others which, after joining the 
stream that descends from Llyn y Gader in the hollow imme- 
diately under the summit of Cader Idris, find their way into the 
estuary some three miles higher up. On this watershed lies a 
lake about half-a-mile long, named Llyn Creigenen, which occu- 
ies a rock basin with two lips at exactly the same level, one at 
its western, the other at its eastern extremity. By the western 
lip a small stream issues which descends rapidly and at one part 
of its course forms one of the branches of the Falls of Arthog, 
well known to visitors at Barmouth. By the eastern lip also, a 
stream, diminutive, it is true (at any rate in the summer 
months), but still quite distinct, issues and descends intoa boggy 
tract, along which it wanders for some two miles, until it joins 
the stream before mentioned from Llyn y Gader. These facts 
are distinctly recorded on the Ordnance map, and I have fre- 
quently verified them myself and pointed them out to others,- I 
think there can be no doubt but that in this instance both of the 
outlets are zatura/, and that a stream must issue from one if a 
stream issues from the other, at any rate at the ordinary level of 
the water inthe lake. It is perhaps, impossible to say that both 
outlets are Zermanent in that secu/ar sense which Prof. Jevons 
seems-to attribute to the word, as circumstances are easily con- 
ceivable under which the flow through the smaller easterly outlet 
might cease; but at any rate for many years, supposing the 
average supply of water to the lake to remain the same, and no 
artificial barrier to be erected, the two streams will continue to 
issue from the lake at all seasons. 
Prof. Jevons remarks that ‘‘ on @ Zyioré grounds it seems very 
unlikely that there should exist any lake with two distinct out- 
flows,” I would reply that, while it is undoubtedly improbable 
that any particular Jake named at random should possess this 
characteristic, it can hardly be regarded as @ priori very unlikely 
that among all the lakes on the earth’s surface there should be 
found here and there one with more than a single outlet. At 
any rate, I would recommend anyone who is sceptical in the 
matter to visit Llyn Creigenen, which is but an easy hour’s walk 
from the Arthog Station on the railway between Barmouth Junc- 
tion and Dolgelly. Rogert B, HAYWARD 
Capel Arthog, Aug. 16 
Cranes in the Gardens of the Zoological Society 
of London 2 
In NATURE of June 26 (antfea, p. 164), Mr. W. A. Forbes 
points out an error in the report of the meeting of the Zoological 
Society for June 15, in astatement that no example of Grus vipio 
(sive leucauchen) had been brought to Europe previously to 
those lately received by that Society. Instead of “ Europe” the 
word ‘‘England” should have stood in the paragraph in 
question, which would then have been correct. 
It is quite true (as stated by Mr. Forbes) that the collection of 
living cranes in the Gardens of the Zoological Society of 
Amsterdam is the finest in the world. At the same time the 
series of these birds in the Regent’s Park is also at the present 
moment very nearly perfect, embracing, as it does, examples of 
all the usually recognised species, with the exception of Grus 
leucogeranus, and G. monacha. 
Of the former of these the Society once possessed a living 
specimen, but the rare G. monacha of Japan has, I believe, never 
yet reached Europe alive. 5 
The following is a list of the Zoological Society’s present 
series of the Gruidze:—2 Common Cranes (Grus cinerea), 1 Brown 
Crane (G. caxadensis), 2 White-necked Cranes (G. deucauchen), 
I Sarus Crane (G. torguata), 1 Australian Crane (G.australa- 
siana), 1 White American Crane (G. americana), 1 Mantchurian 
Crane (G.montignesia), 2 Wattled Cranes (G. carunculata), 
1 Balearic Crowned Crane (Balearica pavonina), 4 Cape crowned 
Cranes (ZB. regulorum), 3 Demoiselle Cranes (Anthropoides virgo), 
August 27 P. 
Colour of Lightning 
I sHOULD be much obliged to any of your readers who would 
give me any information as to the cause of the colour of 
lightning. 
In one of two storms which passed over here yesterday 
evening the lightning was decidedly pink in tint; later in the 
night it had regained its normal yellow or bluish colour. 
Odrey, Aug. 25 H. GEorGE ForDHAM 
Harmonic Causation and Harmonic Echoes 
In reference to the question of ‘‘ Harmonic Echoes,” allow 
me to suggest to those who may have the opportunity of ob- 
servation, how desirable it is that these echo-tones should be 
investigated in a manner to determine whether they are truly 
harmonic or not. There would be no difficulty in testing the 
sounds given in response to the notes of a closed organ-pipe and 
an open one, or the notes of representative musical instruments, 
clarionet and flute. It might be found that the echo at Bedge- 
bury Park would give the octave always, irrespective of the 
particular instrument provoking it; or, on the other hand, that 
it refused to answer to a closed pipe, or gave only the twelfth, 
its proper reply. We should then know whether the echo-tone 
was that of the harmonic or a new fragmental tone consequent 
on the breaking up of the wave of the fundamental or ground- 
tone, by ‘‘ breakers ahead.” 
Now that we are called upon to recognise several varieties or 
classes of musical tone, it is time that the leaders in Science 
came to a general agreemeut upon the use of the term ‘‘ har- 
monic.” Is it to be applied indifferently to ‘* over-tones,” other- 
wise ‘‘partial-tones,” to ‘‘ combination-tones,” to “ concussion- 
tones,” arising from the violence of the shock of sound-waves in 
collision, to ‘‘fragmental-tones” produced out of the wave of 
the ground-tone broken up by obstacles encountered in its 
course or in reflection, and _to “‘echo-tones” which may be 
affiliated to either variety? It seems to me that we risk much 
confusion unless “‘harmonic” is restricted to its earlier usage, 
and applied solely to the ‘‘ harmonic series,”—the tones which 
are the direct offshoots of the fundamental. These tones have 
but one order of succession, and will bear no interpolation: the 
