Fune 17, 1886 | 
NATURE 
153 
altogether its identity with cholera, and assert that it 
is to be found in the mouth of every healthy person. 
Whatever the specific germ may be, it is at least doubtful 
whether any filtration will intercept it; from the ex- 
perience obtained at Valencia and Saragossa it appears 
evident that neither sand nor charcoal will do so. 
In a paper read recently at the Institute of Civil En- 
gineers, Dr. Percy Frankland asserts that the London 
Water Companies do, at the present moment, eliminate 
96 per cent. of all the micro-organisms in the Thames 
water by simple filtration through 3 feet of fine sand. 
This may be so, but it is equally certain that filtration 
through sand, even at a very slow speed indeed, will not 
eliminate the minute particles suspended in waters of a 
deltaic character, and which gives such waters their 
peculiar colour. If sand is incapable of intercepting 
these particles, it may also be incapable of intercepting 
the specific germs or poison that produce cholera in the 
human body. 
Filtration is, at the best, but a doubtful proceeding for 
the purification of water. It is impossible to control 
effectually the speed of the filters ; they vary at every 
moment, and although a mean term may be arrived at 
by taking the area of the filter-beds and the volume of 
water filtered in the twenty-four hours, yet this really 
affords no reliable guide as to the actual speed at which 
the water has passed the filters. It is probable—nay, 
almost certain—that, out of a given quantity of water, 
no two gallons have passed at the same speed, and it is 
possible and probable that one-half of the total volume 
may have passed the filter at double or treble the speed 
of the rest. 
To insure immunity from contamination, the only real 
and practical method appears to be that of capturing the 
water at a pure source and conducting and delivering it 
in such a way as to render it impossible that any specific 
germ or poison should have obtained access to it. Inthe 
matter of cholera, for instance, with the experience of 
Valencia and Saragossa before us, one cannot feel any 
confidence in water which is taken from a river liable to 
so many sources of contamination as is the Thames, and 
it is at least doubtful whether any system of filtration 
would be capable of eliminating cholera-poison from such 
waters. It is extremely probable that simple filtration 
through sand will not do it. 
The very interesting series of letters published by the 
Times on the subject of cholera in Spain afford much 
valuable data as to the causes of the disease, or rather as 
to its mode of propagation. It is unfortunate that the 
writer seems to have gone out with a preconceived idea 
that the cause of the propagation of cholera was defective 
drainage, and consequently to have devoted the greater 
part of his time to the examination of the sewerage of the 
various towns he visited, and of their general sanitary 
arrangements, the water-supply being as a rule relegated 
to the second place. Heappears to be a strong advocate 
for traps, and not to be aware that the best sanitary 
authorities of the present day are beginning to doubt very 
strongly the utility of traps, and to rest their practice 
rather on the thorough ventilation of sewers, the rapid 
discharge of their contents, and a complete disconnection 
between the house drainage and the main sewers. 
It is not too late for some scientific investigator to go 
over the track of the cholera invasion in Spain, to trace 
the progress of the disease in the towns it visited, and 
ascertain all the facts connected with their drainage and 
water-supply, and also, what is not less important, 
examine the conditions of those towns which so far have 
enjoyed a practical immunity from the epidemic. As 
much is to be learned from this negative evidence as from 
the other. 
Pending the discovery by scientific men as to the par- 
ticular germ or poison that creates cholera, such a practi- 
cal examination as I suggest would be of immense value 
to us, by teaching how the propagation of the disease is 
principally brought about, and what are the best means of 
preventing it. GEORGE HIGGIN 
NOTES 
THE Royal Society conversazione, on June 9, was in all 
respects satisfactory. We can only afford to refer briefly 
to a few of the exhibits which attracted the interest of 
the numerous visitors, who were received by Professor and 
Mrs. Stokes. A room was devoted to telephones con- 
nected with the Savoy Theatre, and the company were de- 
lighted to hear the Mikado under such noyel conditions. The 
models of the Romano-British village near Rushmore, on the 
borders of Dorset and Wilts, between Salisbury and Blandford, 
exhibited by Lieut.-Gen. A. Pitt-Rivers, F.R.S., attracted 
much attention. The rare earths from samarskite, gadolinite, 
&c., with illustrations of their phosphorescent spectra, exhibited 
by Mr. W. Crookes, F.R.S., were magnificent. The pumice, 
volcanic ash, drawings, diagrams, &c., illustrative of the effects 
produced by the great eruption of the island of Krakatao, Java, 
in August 1883, exhibited by the Krakatdo Committee of the 
Royal Society, proved very attractive, as did the fine collection 
of astronomical photographs exhibited by Mr. Common, Dr. 
Gill, the Solar Physics Committee, and others. At 9.30 and 10.30 
the stellar and solar photographs were demonstrated, and at Io 
Mr. Common demonstrated the photographs of nebule and 
comets. The first series included the stellar photographs recently 
taken by the Brothers Henry at the Paris Observatory. The 
remaining photographs had reference to solar phenomena, and 
consisted of two series, one from Meudon, the other from Kensing- 
ton ; the former, contributed by Dr. Janssen, had reference to 
the minute portion of the solar surface ; the latter, tosome recent 
attempts to photograph the spectra of sunspots and prominences, 
The photographs of planets, comets, and nebulz, exhibited by 
Mr. A. A. Common, F.R.S., consisted of (1) series of photo- 
graphs of Saturn; (2) series of photographs of Jupiter; (3) 
photograph of Mars ; (4) nucleus of the great comet 1882; (5) 
the Dumb-bell Nebula; (6) the Crab Nebula; (7) the Spiral 
Nebula ; (8) the Great Nebula in Andromeda ; (9) series of photo- 
graphs of the Great Nebula in Orion, with exposures of I min. to 
80 min. (the above were all taken with the 3-foot reflector at 
Ealing) ; (10) recent photographs of Saturn, Jupiter, and the 
nebulz in the Pleiades, by the Brothers Henry. 
AT the annual meeting of the American Academy on May 25, 
it was voted to present the Rumford gold and silver medal to 
Prof. Langley, of the Alleghany Observatory, for his researches 
on radiant energy. 
THE thirteenth annual meeting of Scandinavian naturalists 
will take place in Christiania between July 7 and 12. 
WHILE Mount Etna has again quieted down during the past 
week, volcanic energy has manifested itself at the Antipodes in 
an unexpected quarter. Though the North Island of New 
Zealand is known to be greatly volcanic, and has in Tongariro 
an active volcano, there has been no destructive eruption 
within the memory of man. The eruption therefore tele- 
graphed on June 10 was quite unexpected, It occurred in the 
Tarawera district, on the east side of the Tarawera Lake, lying 
in a line between the Bay of Plenty and the mouth of the Wan- 
ganui River, It is a long way north from Tongariro, and in the 
midst of the wonderland of Rotomahana’s hot springs and many- 
coloured terraces. The country is stated to be in a disturbed 
state for many miles around, and it is estimated that a hundred 
natives and ten Europeans have perished. 
A sHock of earthquake was felt on Friday night at Sandy 
Hook and Coney Island, New York, U.S, 
