NoveEMBER 12, 1903] 
NATURE 
31 
eR ——_—_—_ EEL a ne 
Explosive Action of Lightning. 
Tue following particulars of the circumstances attending 
a lightning flash are perhaps worth recording. 
A cedar tree (deodar) 50 feet high stood at a distance 
considerably less than its own height from a house at 
Englefield Green. The lady of the house was sitting watch- 
ing the storm, but in such a position that she could not 
see the cedar, but could see a large part of an Araucaria 
(the common ‘‘ monkey puzzle ’’) just outside her window, 
and only 30 or 4o feet from the cedar. While watching 
this tree the lady saw, as she thought, a “rod” or 
“ stick ’? of fire come crashing down through its branches 
—hbeating them down so that she distinctly saw them re- 
bound. This was accompanied by a fearful noise as of a 
‘thousand pistol cracks, beside which, however, the lady 
had an impression of hearing the branches of the Araucaria 
beating. together, and immediately afterwards a cloud as 
of steam rose from the lawn on which the trees stood. 
It was found that the cedar tree had been wrecked entirely. 
About 15 feet of the top was broken off, and apparently fell 
straight down—sticking in the ground almost vertically— 
close to the stump of the tree. The main portion of the 
trunk, to about 4 feet from the ground, was roughly split 
in two—falling right and left—one half being further burst 
into several pieces. There was the usual ‘smell of 
sulphur,’’ but no sign of scorching on either of the trees. 
A gentleman who saw the flash from a distance of about 
one-third of a mile noted that it was a straight (non-forked) 
flash from a small cloud low down. Other observers noted 
flashes of a similar character during the same storm. 
The cedar tree was in vigorous growth, full of sap, and 
well above its immediate surroundings, but there were elms 
and a lime tree of greater height within fifty yards of it. 
The movement and the ‘‘ fire’’ in the branches of the 
Araucaria seem to me to suggest an electrostatic effect—a 
side splash—rather than the mere reflection of the flash 
which struck the cedar. Could the beating down of the 
branches be explained as the result of the sudden pulse in 
the air? What produced the cloud of ‘‘ steam’’? It would 
be interesting to have the opinion of an authority on light- 
ning discharges with regard to these points. 
R. A. WEsT. 
Ordnance College, Woolwich, October 27: 
The ‘ Sky-coloured’”’ Clouds. 
DurinG this summer I have seen only one display of the 
““sky-coloured ’’ clouds, or ‘‘ night-shining clouds ’’ as the 
fate Herr O. Jesse used to call them. It was on July 8, 
and was a bright display, the brightest I have seen for some 
years. It is rather singular they did not appear on other 
occasions so far as I have observed, and no mention of them 
has been made in your periodical. It may be that now 
Herr Jesse is deceased there has not been such a good and 
systematic watch maintained as formerly, or else, if they 
have been observed abroad, notices have not been copied 
into English papers. Whether the brilliancy of this one 
display was connected with the eruptions in the West Indies 
is a matter of conjecture. The volcanic dust continues to 
be very visible in the sky in producing the great corona 
round the sun all day. T. W. BackHOUSE. 
_ West Hendon House, Sunderland, October 28. 
THE GEOLOGY OF VANUA LEVU.! 
ay es LEVU, one of the two principal islands in 
' the Fiji archipelago, according to Mr. Guppy’s 
summary of previous investigations, has received less 
notice than Viti Levu, or even some of the smaller 
islands. The late Prof. Dana made a small collection 
ofits rocks in 1840, and published some observations 
‘on its geology. It was visited in 1878 by Mr. J. 
Horne, of Mauritius, but no collections were made by 
him, by the Challenger, or by investigators under the 
1 “‘Qbservations of a Naturalist in the Pacific between 1896 and 1899.” 
By H. B. Guppy, M.B., F.R.S.E. Vol. i. Vanua Levu, Fiji. Pp. xix+392; 
illustrations and map. (London: Macmillan and Co., Ltd. ; New York : 
* The Macmillan Co., 1903.) Price 15s. net. 
NO. 1776, VOL. 69] 
direction of Prof. A. Agassiz, so that it offered a very 
promising field of research, which occupied Mr. Guppy 
for two years. The results, so far as concerns its 
geological and general physical features, and the 
petrology of its rocks, are described in the present 
volume, with reproduced photographs and other illus- 
trations. 
The long irregular outline of Vanua Levu contrasts 
strongly with the comparatively rounded one of Viti 
Levu. Its length is about 98 miles, with a breadth 
averaging 15 to 20 miles, its estimated area being 
about 2400 square miles, nearly equal to that of the 
county of Devon, while its maximum elevation is 
almost 3500 feet. Both this island and Viti Levu rise 
from a submarine plateau, in shape a broad irregular 
ring, broken in one place. An elevation of less than 
roo fathoms would convert the whole area into one 
great mountainous island, pierced on the southern 
side by a fjord more than 200 fathoms deep. This 
platform Mr. Guppy considers to have been built up 
from the deeper ocean floor by submarine lava flows 
and associated deposits, and Vanua Levu as a compo- 
site island, formed, during a long period of emergence, 
by the union of a number of large and small islands, 
the products of submarine eruptions. The process 
probably began in the later Tertiary period, and 
volcanic eruptions have now ceased, but hot springs are 
not uncommon, though limited to regions where basic 
rocks occur. They are also restricted in vertical range, 
for they have not been found above the 300 feet con- 
tour line. Their temperature mostly ranges from 100° 
to 150° F., reaching 180° only in one case, the latter 
group precipitating siliceous sinter. Mr. Guppy 
thinks these springs are largely sunvlied by the ‘‘ soak- 
age’ of the heavy rainfall in the mountains; if so, 
there must be rapid local rises in the underground 
temperature. A submergence of 300 feet would bring 
the sea over a considerable tract, chiefly basaltic plains, 
which are obviously continuous with the submarine 
plateau. One of 1000 feet would greatly reduce and 
indent the remaining axis of the island, while 800 feet 
more would convert it into a few scattered islets, which 
would represent the nuclei of the present composite 
Vanua Levu. This mode of building accounts for the 
irregularities of its physical structure, in which respect 
it contrasts markedly with the other large island, Viti 
Levu. 
Proof of this great elevation is found in the occur- 
rence of muds and tuffs with marine organisms up to 
at least 2000 feet above sea-level. Shelly and foram- 
iniferal limestones, composed, as so often in tropical 
islands, partly of reef débris, partly of more or less 
broken. shells of Mollusca, partly of Foraminifera, 
occur up to a height of r1oo feet, and they sometimes 
overlie palagonite tuffs and clays, also foraminiferal. 
Pteropod ooze, containing a large amount, of pala- 
gonitic débris, is found up to about 500 feet, but 
volcanic muds, which are very abundant on the 
basaltic plains in association with the lava flows, reach 
the former elevation, while tuffs, sometimes agglomer- 
atic, may be traced up beyond 2000 feet—all these con- 
taining Foraminifera. An instance of these deposits 
is shown in the illustration. Raised coral reefs are not 
very common, and appear to be limited to a vertical 
range of about roo feet above sea-level, so that in this 
respect Vanua Levu contrasts strongly with Viti Levu. 
But Mr. Guppy thinks this scarcity to some extent the 
result of denudation, for he has found silicified corals, 
representing reef-forming types, lying about on the 
surface, abundantly in some places, together with 
nodules of chalcedony and other siliceous concretions. 
These, however, do not more than double the vertical 
range, so that during the actual building of the 
island circumstances were not favourable to reef- 
