1893. NOTES AND COMMENTS. 407 
CHOLERA. 
Tue May number of the New Review has a sensible and readable 
article by Dr. Robson Roose on the propagation and prevention of 
cholera. Numerous cases are cited in illustration of the intimate 
relation between the water supply and cholera outbreaks, and hence 
the supreme importance of the purity of water used for drinking. 
The author does well in pointing out that dirty filters are worse than 
none at all; unless it is from time to time cleansed or renewed, 
fairly good water may actually take up impurities from the filter. If 
charcoal be the agent it should be boiled occasionally, say once a 
month, and then dried in the sun or an oven. Spongy iron filters are 
recommended for general use as being cheap and easily renewed. 
The fact that water is cool and sparkling does not imply purity. An 
outbreak in Golden Square in 1854 was traced to a well, the water 
from which was much liked for having these characteristics, but on 
examination was found to be contaminated by leakage and filtration 
from a cesspool. The general rules for prevention of the epidemic 
are those of ordinary hygiene, cleanliness in all things, moderation, and 
care in diet and exercise. The fact that more than five-and-twenty years 
have passed since cholera gained a footing in this country, though 
it has from time to time reached our ports, may fairly be attributed 
to the improved sanitary conditions which now obtain in all our large 
towns. 
A stupy of the range of the Molluscan genus Placostylus has lately 
led Mr. C. Hedley to generalise in reference to the ancient geography 
of the region of New Caledonia, the Solomon Isles, New Hebrides, 
and Fiji Isles, and their connection with New Zealand (Proc. Linnean 
Soc. N. S. Wales, ser. 2, vol. vii., 1893, pp. 335-339). He thinks 
that these islands form part of a shattered continent, never connected 
with, or populated from, Australia, but rather deriving their fauna 
from Papua wid New Britain. The presence of genera common to 
Australia and New Zealand is explicable on the ground that they 
migrated, not from the one territory to the other, but each from a 
common source, New Guinea. New Zealand and New Caledonia 
seem to have been early separated from the northern archipelagoes 
and to have ceased to receive overland immigrants therefrom. 
Finally, the Fijis appear to have remained to a later date in com- 
munication with the Solomons, though severed from that group 
before the latter had acquired from Papua much of its present fauna. 

Tue problem of stocking a pond with fish receives an unex- 
pectedly bold solution in our contemporary Iilustvated Scientific Facts 
(April 15); itis there said that, as the bottom of many ponds con- 
sists of soil which was once the bottom of the sea, it probably 
abounds in spawn deposited, say, by the fishes of the Old Red 
