602 
NATURE 
[ Oct. 22, 1885 
period two of these cones have been destroyed by the 
terrible eruption of 1883. As our authentic records of 
Java only date back 300 years, we have absolutely no 
data respecting anything that occurred in the first three 
of these periods. We have accounts of an eruption of 
the Perbvewatan in the year 1680 from two travellers— 
Vogel and Hesse—to which I drew attention in the 
Algemeen Dagblad van Ned. Indie of May 23, 1884; but 
they say nothing as to whether that crater was formed at 
that time or had been already active. After a rest of 203 
years the Perbvewatan became again active in May, 
1883, and the Danau joined it in activity during the 
following June, forming the principal crater in the centre 
of the old volcano. In August, at the great eruption of 
the 27th, this part of the volcano was again destroyed ; 
the Perbvewatan and the Danau, with the northern half 
of Rakata Peak, disappeared, and the site of the old 
crater is now covered by the sea between the islands 
Lang, Verlaten, and Krakatdo. 
If the volcano resumes its activity, which is to be 
expected since the island lies on such a favourable point 
for eruptions, then small islands will appear between the 
three already mentioned. Krakatdo has been at rest 
since 1883, although it has erroneously been reported to 
be active. The roll of thunder and the flashing of light- 
ning over the ruins of the crater wall have been 
mistaken for the action of subterranean forces, while the 
volcanic dust swept off from the crumbling summit by the 
wind appears at a distance like smoke. 
A very curious and interesting feature of the recent 
eruption of Krakatao was the ejection of fragments of 
underlying sedimentary rocks. The base of the Krakatao 
volcano, and in general the entire bottom of the Straits 
of Sunda, consists of eruptive rocks of the miocene 
period covered with horizontal layers of diluvial and 
recent marine deposits, the materials of which have been 
derived from the various volcanoes in the vicinity. 
The first volume of Verbeek contained a valuable 
report from his colleague, Mr. J. A. Schuurman, on the 
phenomena of the eruption of May, 1883, as observed by 
himself, and the second volume has a lengthy and minute 
description by the mining engineer, Mr. J. W. Retgers, of 
his microscopical examination of the ash which fell at 
Buitenzorg, and of the various substances thrown out by 
the eruption of 1883, as well as of the older rocks. 
A portion of the pumice which covered the sea after 
the eruption was carried westward by winds and currents 
and driven on the shores of various islands, even so far 
as the east coast of Africa. Another portion, which 
floated in the bays of Semangka and Lampong for several 
months, being driven in the beginning of 1884 by westerly 
winds along the coast of Java toward the Moluccas and 
Australia, is at present encountered in the Pacific Ocean 
between the Caroline and Marshall Islands. The author 
has calculated that this pumice will arrive on the west 
coast of America at Panama early in 1886. 
With regard to the spherical bodies of a calcareous and 
clayey nature, called “ Krakatad marbles,” found lying 
loosely on the surface, Mr. Verbeek at first supposed 
them to have been formed by the rotary motion of 
particles ejected from the volcano, but as they were after- 
wards found imbedded in ejected fragments of claystone 
and matls, this theory must be given up ; he considers it 
possible that there may have been concretions in the 
tufa, although their presence in rock sometimes quite 
destitute of lime is certainly surprising, and this form of 
concretions has not been observed hitherto. 
The chemical analyses of the rocks of Krakatao can be 
fully relied upon, as they have been made by Dr. Cl. 
Winkler, Professor of Chemistry in the well-known 
Mining School of Freiberg, in Saxony. Dr. P. J. van 
der Stok, Director of the Meteorological Observatory at 
Batavia, proves that the disturbance in the position of the 
magnetic needle observed during the falling of volcanic 
dust was due, not to the eruption, but to the presence of 
magnetite therein, since the disturbance only lasted during 
the shower of ashes. 
The low temperature observed at that time at Batavia, 
Buitenzorg, Kroé, Moeara-Doea, Bandar, and elsewhere 
was not due, according to hygrometrical observations, to 
the evaporation of the humidity of the ash; near the 
volcano and on ships in the vicinity it was oppressively 
hot, but the ashes thrown into the icy regions of the 
upper air and falling at a distance from the volcano had 
become cooled in their passage. Heavy electrical dis- 
charges occurred continually in the ash cloud around 
Krakatao. On Java’s First Point and at Flat Point the 
lighthouses were struck by lightning. 
On Sunday, May 20, 1883, all Batavia was in great 
commotion as to the cause of the mysterious sounds and 
detonations which apparently came from the west and in 
fact did come from Krakatao. At Serang and Anjer, 
which are situated much nearer to the volcano, no sounds 
had been heard. Again at Batavia on the morning of 
Monday, August 27, after the tremendous detonation at 
8h, 26m., the eruption seemed to have ceased ; they heard 
nothing at all of another enormous explosion which took 
place between 11 and 12, as reported from Middle and 
East Java. The explanation of this curious phenomenon 
is that earlier in the morning an ash cloud like a gigantic 
lamp-shade settled over the volcano, extending as far as 
Bandong, and that the quantity of these ash particles 
floating in the air prevented the transmission of sounds. 
Above the ash cloud the detonations were transmitted in 
all directions, but naturally were most distinctly heard 
to the windward. ‘The farthest points where the sounds 
have been heard are Doreh, in New Guinea, some points 
of Central Australia, among others the telegraph stations 
of Daly Waters and Alice Springs, the islands of 
Rodriguez and Ceylon. Accounting for the difference in 
time and taking the rate of transmission of sounds, the 
author has calculated for different places which grand 
detonation in particular has been heard. The detonation 
of Monday morning, 5h. 30m., has been heard in Australia ; 
that of 1oh. 2m. a.m. has been heard at Banca, Billiton, the 
west coast of Borneo, the southern and eastern divisions 
of Borneo, Bawean and Banda; that of 1oh. 52m. a.m. at 
Riouw, Middle and East Java, Bali, &c. ; the last two 
detonations have not been noticed at Batavia and Buiten- 
rorg. The area within which the explosions have been 
heard is represented on a map; it amounts to one- 
fourteenth of the whole surface of the globe—a quite 
extraordinary transmission of sound over so large a space. 
From the vibration of the air caused by the heavy de- 
tonations houses, doors, windows, clocks which hung 
against the walls, objects which stood on cabinets or were 
suspended from the ceiling were set trembling; but the 
swinging movements given to hanging objects by earth- 
quakes have nowhere been observed. That some walls 
have been cracked, and houses been damaged so as to be 
no longer habitable, can be accounted for, according to 
the author, by the probability that they were already 
weak, and thus had an opportunity of showing it. 
The greatest air-disturbance caused by the eruption 
has transmitted itself as a regularly moving atmospheric 
wave, with Krakatao as centre, over the whole earth ; and 
to the discussion of this entirely new phenomenon the 
author has devoted about seventy pages. With the 
assistance of very accurate barograms from Sydney, 
N.S.W., he calculated the heaviest explosion and fixed it 
at Ioh. 2m. a.m. Krakatad time. The same result has been 
arrived at by another calculation based on the markings 
of the indicator of the gasworks at Batavia. That indi- 
cator marked fifteen oscillations, corresponding with as 
many explosions, of which the four severest occurred in 
the forenoon of Monday, August 27, at 5h. 30m., 
6h. 44m., toh. 2m., and toh, 52m., Krakatao time. 
Of these four, that of 10h. 2m. am. was by far the 
