May 13, 1886] 
NATURE 
313) 
_ we see, that the 184 parts of benzene require 56°8 parts 
of oxygen for the oxidation of their carbon and hydrogen 
to carbonic acid and water. This oxidation or combustion 
takes place at the moment of explosion at the expense of 
the 56°8 parts of oxygen, contained in the rest of the 
mixture—the 81°6 parts of nitric peroxide. No other ex- 
plosive now in use (including blasting gelatin) contains 
weight for weight a greater amount of combustible matter, 
and as an explosion of ¢ese bodies is simply a sudden 
combustion, I again beg to draw attention to the fact that 
the oxygen available for combustion in gun-cotton is most 
probably not more than 32°3 per cent. and in nitro- 
elycerin 42°3 per cent.,' while in this case we have with- 
out a doubt 56°8 per cent. Hence no other explosive now 
in use can rival this and similar mixtures in power, as I 
published in 1873. They still remain the most powerful 
explosives known. 
“Tt hardly need be said that an explosive of this nature 
consists of two parts—an oxidising and a combustible 
agent--and that Mr. Turpin with the same waiveté lays 
claim not only to the first, but also to the latter half of 
the subject. 
“ None of my s7/ety-explosives are licensed in England, 
though many of them, when mixed, are much less sen- 
sitive to concussion than common gunpowder. 
“In April 1884 the French military authorities were 
busy near Rochefort with shells of the ‘systeme Turpin.’ 
These shells, so my informant said, were made of such a 
size, and possessed such a prodigious power, that a ship 
struck by one of them would inevitably be sent to the 
_ bottom of the sea, even were she the strongest ironclad 
afloat. It is devoutly to be hoped that those whose office 
it is to provide for the defence of the British Navy w2?/ 
be ready in the hour of need to serve out shells, filled 
with an explosive of equal force or better still with some- 
pare, Superior, approaching more closely the ‘beau 
idéal. 
MR. VERBEEK ON THE KRAKATAO DUST- 
GLOWS 
“AS it appears from the letter of Mr. Douglas Archi- 
bald in NATURE of April 29 (p. 604) that some 
doubt exists as to the quantity of volcanic dust ejected 
during the Krakatdo eruption in 1883, it may not be in- 
- Opportune to give an abstract of what Mr. Verbeek—the 
_ best authority on the subject—says in the second part of 
his book. The mistake in the number of cubic kilo- 
metres—which Dr. Riggenbach or his critic magnified 
from 18 into 150—may possibly have arisen from the 
comparison Mr. Verbeek draws between the quantity of 
volcanic substances ejected by the Tambora in 1815 and 
_ that ejected by Krakatao. 
| Junghuhn estimated the quantity of ashes ejected by 
the Tambora in Sumbawa at 318 cubic kilometres, but 
Mr. Verbeek reduces it by calculation to about 150, 
though he adds that the data are insufficient to form a 
really correct estimate. It is certain, however, that 
the quantity was considerably larger than that ejected 
by Krakatao. To calculate this quantity Mr. Verbeek 
made observations everywhere on the islands and 
_ along the coasts of the Straits of Sunda; while the 
thickness of the ashes which fell into the sea was 
| computed according to the difference in the depths 
of the sea before and after the eruption, a difference which 
| $reatly varies, and amounts in some places to 40 metres, 
if not more. Wherever some doubt exists for want of 
previous accurate deep-sea soundings, Mr. Verbeek gives 
a 
__* OF these, by the bye, only 38°8 per cent. can be utilised for want of fuel, 
as pointed out by me in my patent of 1871, and verified four years later by 
che force of Nobel's blasting gelatin, in which the excess of 3'52 per cent. 
‘oxygen is utilised by the dissolved gun-cotton, an explosive too rich in 
m. See Abbot's table, p. 17, in ‘The Hell-Gate Explosion near New 
de and so-called ‘ Rackarock,’ with a few words on so-called ‘ Panclastite,’” 
‘HH. Sprengel. London: E. and F. N. Spon, 1886. 
the lowest figures. These observations are all illustrated 
by maps. Mr. Verbeek estimates the quantity of ejected 
material which fell round the volcano at 18 cubic kilo- 
metres at least. The possible outside margin would, 
however, not exceed 3 cubic kilometres. Of this 
quantity, two-thirds, or 12 cubic kilometres, lies within 
a circle with a radius of 15 kilometres drawn round 
Krakatao, one-third, or 6 kilometres, outside it. Of the 
finer ashes a large quantity were already, during the first 
three days, blown into the sea, as appeared from observa- 
tions made on ships; and Mr. Verbeek assumes that 
considerably less than 1 cubic kilometre remained floating 
in the upper regions of the atmosphere. This quantity 
would correspond to a layer of o’002 millimetre thickness 
divided over the whole surface of the earth, or of o'004 
millimetre over the temperate zones only. 
Such an infinitesimally thin layer could hardly have 
been the principal cause of the atmospheric phenomena. 
They must be accounted for in a great measure by 
the large volume of aqueous vapour ejected by 
Krakatdo, the amount of which lies, unfortunately, 
beyond all calculation. We have to deal with two dis- 
tinct phenomena, as Prof. Michie Smith also has shown 
by the two different spectra, and these phenomena had 
different causes: thus, the blue and green tints of sun 
and moon, which were specially observed during the first 
month after the eruption, and only in places close to the 
equator, must be principally ascribed to the so/zd particles 
in the volcanic ash-cloud, as various observations have 
shown that these are the main cause of the special ab- 
sorption of the rays of light by which the sun appeared 
blue and green; the aqueous vapour may have increased 
the phenomenon, for it is known that the sun can look 
bluish through mist. It cannot be said to be a proof 
to the contrary that Mr. Lockyer saw the sun green 
through the steam which escaped from the funnel of a 
steamer, for probably a quantity of ash and soot-particles 
escaped from the funnel at the same time, and it is possible 
that the sun appeared green from that very fact. The steam 
was thus in the identical condition of our volcanic cloud. 
It was only in the beginning after the eruption, before 
the ashes had spread very far, and when, therefore, their 
density was greater, that they were able within a limited 
space to give green tints to the sun. This phenomenon 
ceased when the ashes were dispersed further round the 
globe—in the northern hemisphere by the south-west, in 
the southern hemisphere by the north-west winds—and 
when probably also a portion of them fell gradually on 
the earth. 
The crimson after-glows which soon followed the erup- 
tion were observed a¢ the same tzme over a much larger 
area than that within which the blue and green sun was 
geen at successive periods, and they are believed by Mr. 
Verbeek to have been caused mainly by the masses of 
aqueous vapour thrown out by Krakatao, and which formed 
the greater part of the volcanic cloud. This vapour, after 
condensing and freezing in the higher and colder regions 
of the atmosphere, produced the remarkably beautiful 
sunsets, while the ashes may have intensified the pheno- 
menon, besides serving as a centre of condensation for 
the vapour. The real cause of the crimson glows was 
therefore probably the same as that of the evening red, 
their intensity being a consequence of the extraordinary 
quantity of vapour in the upper regions emitted by 
Krakatao. 
THE PARIETAL EVE OF HATTERIA 
So little time ago, whilst engaged in work upon 
FHlatteria punctata, | found a curious sense-organ 
embedded in the substance occupying the parietal fora- 
men, but was unable at the time to examine the specimen 
further ; Prof. Moseley has kindly directed my attention 
to a short paper published in the Zoologischer Anzeiger 
