Fune 23,1870] 
NATURE 
143 
then a last look into the huge abyss, we run easily down the 
side of the cone, and are in a few minutes at the Casa degli 
Inglesi again. Here we turn off towards the eastern side 
of the mountain, and soon come upon the edge of the Valle 
del Bove, to enjoy perhaps the most remarkable spectacle 
in Europe. We find ourselves now on the summit of 
an almost vertical cliff, nearly 4,000 feet high, which con- 
stitutes the head of an enormous cleft or valley, about eight or 
ten miles long by four or five broad ; it is as if a piece, consti- 
tuting about one-sixth part of the mountain, had been cut 
out of it. On either side it is bounded by cliffs of from one to 
three thousand feet high, and consisting of layers of lava and 
ashes traversed by dykes of basalt, trachyte, &c. ; several vol- 
canic cones are seen in it, of which Monte Simone, to the 
northern side, with its lava of 1811, and Centennario, Calanna, 
and Giannicola to the southern side, with the barren black lava 
of 1852, are the most noticeable ; thisimmense depression was 
caused, according to the opinion of Sir Charles Lyell and of 
Gemmellaro the great Sicilian vulcanologist, by the subsi- 
dence of an ancient felspathic volcano, which must, according 
to calculations made from the inclination of its lava currents, 
have been much higher than the modern pyroxennic one. (La 
Vulcanologia dell’ Etna, del Professore Carlo Gemmellaro ; 
Catania, 1858.) Such a subsidence is well illustrated on the 
small scale by the Cisterna, a round hole about 300 yards in 
diameter, and at least 200 feet deep, which was formed precisely 
in the manner just mentioned during the eruption of 1792, and 
which we can see on our way back to the Montagnola; indeed, 
when we consider how much material is ejected during the 
various eruptions in the form of lava and of ashes, &c., we see 
that it would be strange if subsidences, and great ones too, did 
not happen occasionally. 
We now descend quickly, finding our last night’s tracks 
behind the Montagnola, and by 10.30 are off the snow, and 
find the mules ready for us. In returning to Nicolosi we are 
able to observe the various lava currents, and to study their 
sections in the channels of the streams which rush down during 
the melting of the snow in the summer months, and also to notice 
the gradual change in the vegetation which the darkness’ pre- 
vented our remarking during the ascent. 
We find the heat more and more oppressive, and are afflicted 
with very severe headaches; on arriving at Catania we find it 
covered by a dense fog (an extremely unusual occurrence there), 
and so the congratulations on our safe arrival are mixed with 
wishes that the weather had been more favourable. 
In a future communication some remarks will be made on a 
few observations taken during this excursion. 
W. H. CorFIELp 
Paraplegia in Kangaroos 
SOME time ago I obtained from Mr. Fairgrieve the bodies 
of two Kangaroos, male and female, which died during the visit 
of Wombwell’s Menagerie to the West of Scotland. In the 
female, which I received first, there was extensive ecchymosis in 
the nuchal region strongly suggestive of bites inflicted by her 
cage companions. To this I was disposed to refer the softening 
of the cervical spinal cord, which struck me when removing the 
brain. On visiting the menagerie, however, I found that her 
male companion was completely paraplegic, and that he had 
exhibited the same symptoms. ‘The paraplegia had been pro- 
gressive, and at the date of my visit, respiration was markedly 
thoracic. The animal was excited, but I could not satisfy my- 
self whether this indicated cerebral disturbance or arose from the 
contagion of fear, a younger specimen in the same cage being 
much alarmed at my approach. The animal died at some dis- 
tance from Glasgow. I made a careful post-mortem, and found 
no lesion save in the spinal cord and medulla oblongata. The 
removal of the cord was difficult, on account of the thickening 
of the membranes, and their adhesion to the bony walls of the 
canal. The cord was not merely softened; it was semifluid 
as far up as the origin of the cervical plexus, and welled out like 
thick cream from an accidental puncture of the sheath. Dr. 
Joseph Coats who assisted me in the examination, failed to detect 
any fatty degeneration of the nervous tissue. Its disintegration 
was, however, very complete. The other organs were healthy, 
and the body was well nourished. The disease was manifestly 
-of short duration, and I can only hazard this conjecture as to its 
cause, that the cage was placed at the angle of the square formed 
by the cars, and that its inmates were thus exposed to draughts 
and damp, giving rise to acute meningitis. As, however, an 
Australian sportsman informs me that something of the same 
kind has been observed in Kangaroos kept in confinement, and 
thus deprived, to a large extent, of their customary exercise, I 
ask space for this abstract of the case, in hope that some of your 
contributors may be able to throw light on an interesting patho- 
logical question. 
JouN Younc, M.D., 
Keeper of the Hunterian Museum 
Glasgow University 
Geology and the Chatham Dockyard 
BeELow the Alluvial deposit of St. Mary’s Island is a very 
irregular surface of gravel, varying in thickness from 2 to 12 feet, 
and composed of flints but little rounded, and pebbles of Ter- 
tiary Sandstone ; beneath the gravel is the Chalk. Now, the 
success of the Chatham Dockyard Works depends upon the 
stability of foundations that are built on piles driven into the 
underlying gravel, through which percolate considerable streams 
of water ; this water must denude the chalk to an appreciable 
extent and form pot-holes, and the subsidence of the works can 
but be a matter of time. I can form no idea of the rate at which 
the Chalk would be denuded under the above conditions, as I 
am not aware of any experiments having yet been made on the 
** Action of Water on Chalk.” 
R. C. Harr 
Dust and Disease 
PERMIT me to add my mite to Mr. Horace Waller’s theory 
respecting the utility of mosquito curtains in warding off fever, 
generated by the miasma of decaying vegetation. 
For the last twenty-five years I have held to this opinion, and 
acted on it in all my wanderings in the jungles of Ceylon, on the 
east coast of Africa, and in New Zealand, and I am convinced 
of its great utility. I have always likened it to Davy’s ‘‘safety 
lamp,” and I believe that over and above the “ sieve-like” pro- 
perty, which a few days’ use imparts to it, its value is great as 
warming the air which passes through its meshes, and keeping 
the temperature within it more steady and equal. 
When the body is relaxed in sleep and the pores of the skin — 
act freely, then is the time that the deadly miasma, cold and 
damp, even in the tropics, seizes on its victim. What jungle 
traveller does not know the feeling of the air an hour and a half 
or two hours before daylight? But the warmth from the body 
and breath within a well-secured mosquito net, I think effec- 
tually protects the sleeper. 
This morning I compared the temperature outside and inside 
my mosquito net, and found it differ 8°, being 62° outside and 
70° within, and even this was not a fairtrial, for the bed is a 
large double one (two persons in it), exposing a large surface 
to the external air; the mosquito curtain being the largest sized 
Net that can be got (and not Zezo) which I would advise for 
a travelling curtain in fever latitudes ; and moreover, as our mos- 
quito season is past, not tucked in allround as a well-secured 
curtain should be, yet with all these disadvantages the tem- 
perature inside was 8° warmer. 
Then, again, who doubts that the body, invigorated by sound 
sleep, is not more able to resist disease in the day-time? Without 
a net in mosquito lands I find sleep impossible, and I suppose 
others do the same. 
Let me therefore raise my voice in favour of the mosquito 
curtain, and advise all travellers in fever countries to look 
on it as their sheet anchor. E, L. Layarp 
Cape Town, Cape of Good Hope, 
May 3 
HEINRICH GUSTAV MAGNUS 
1a giving expression to the sympathy generally excited 
by the loss of Magnus, Professor Tyndall has raised 
the interest of the British public in a philosopher’s life, 
simple, yet most eminently useful. At the-present moment 
a mere outline of it is all we can venture to offer. Unable 
to appease, it may yet prove sufficient to keep up the inte- 
rest in Magnus’s life until a fuller biography will do 
more ample justice to his merits. 
Heinrich Gustav Magnus was born on the 2nd of May, 
in the year1802. Four years later, Berlin, his native town, 
