yune 17, 1886] 
NATURE 
149 
Reports include a continuous hourly record of the more 
important elements of the climate of Hong Kong. The 
buildings are erected on the peninsula of Kaulung, facing 
the harbour, on the top of Mount Elgin, a small eminence 
rising from the plain to a height of about 110 feet above 
mean sea-level. It may also be noted that the ground 
has been carefully turfed where the instruments are 
placed. In addition to the usual tabulations and their 
averages, the Monthly Report gives a carefully observed 
log of non-instrumental phenomena, such as dew, fog, 
unusual visibility, halos, and thunderstorms. 
The results show that the amplitude of the daily range 
of the barometer is greatest from November to February, 
when the rainfall is least and the air driest, the mean 
difference during these four months between the morning 
maximum and afternoon minimum amounting to 0'102 
inch. On the other hand, the mean of the four months 
from June to September, when the monthly rainfall nearly 
equals 12 inches, only amounts to o'069 inch. The 
diurnal range of temperature is small, being for the year 
only 5°5, the maximum, 7°'2, occurring in December, and 
the minimum, 40, in February. The daily minimum occurs 
at all seasons shortly before sunrise,and the maximum from 
1 to 2 p.m. during the dry season, but an hour later during 
the wet season. The hourly means for the tension of the 
aqueous vapour are very interesting, as showing very 
clearly for those months when the sunshine is daily prac- 
tically constant and the air relatively dry a minimum 
period during the hottest hours of the day ; whereas when 
the sunshine is much interrupted, the rainfall frequent, 
and the air moist, the daily maximum tension occurs at 
these hours. 
For the twelve months beginning March 1884, the 
greatest amount of sunshine was from noon to 2 p.m., 
and the least from 4 to 5 p.m., the former being per hour 
nearly double the latter. During the 22 months the 
greatest monthly number of hours of sunshine for any hour 
of the day was 26°3 hours from 9 to 10 a.m. of October 
1884 out of a possible 31 hours. From midnight to noon 
the mean monthly rainfall has been 4°98 inches, but from 
noon to midnight the amount has only been 2°73 inches. 
The four consecutive hours of largest rainfall are from 5 
to 9 a.m., amounting to 1’gI inch, and the four consecutive 
hours of least rainfall from 8 p.m. to midnight amounting 
only to 0’76 inch, or considerably less than half the former 
time of the day. The diurnal period of the rainfall of 
Hong Kong is remarkable as showing the maximum fall 
during the period of rising temperature, and the minimum 
when temperature is rapidly falling, the amounts for the 
six hours ending noon being 2°66 inches, and for the six 
hours ending midnight 1°24 inch. Future observations 
will doubtless modify in some degree the curve of daily 
rainfall, but from the general accordance of the fall of the 
individual months with what is indicated above, it is not 
likely that the change of the curve will be very material. 
The daily curves for the winds, both as regards velocity 
and direction, are very decided. The daily curve for 
wind velocity has, for Hong Kong, owing to its peculiar 
position with reference to the island and the continent, 
peculiar features of its own. Thus for the year the maxi- 
mum yelocity extends from 10 a.m. to 2 p.m., the means 
for these four hours being the same, while the minimum 
velocity extends from 6 to 10 p.m., the hour of least 
movement being from 7 to8 p.m. From midnight the 
wind rises to the daily maximum at 10a.m. The month 
of greatest force of wind is March, and of least August, 
the air-movement in the former month being nearly 
double the latter. As regards direction the wind is about 
E.N.E. in the winter and E.S.E. in the summer season. 
For the whole year, the mean direction is E. 3° S., and 
the diurnal variation from E. 5° N. at midnight to E. 15° S. 
at noon, the mean yariation being thus through 20°. 
During 1884 the total distance travelled by the wind was 
103,237 miles, and of these 63,349 miles, or more than 
half the whole, was east wind. The least frequent wind 
is N.W., which showed only 2053 miles. 
At a distance of about two miles from the Observatory 
an important station has been established on Victoria 
Peak, at which observations are made at 10 a.m. and at 
4 and Io p.m., and the results are published 7” exfenso in 
the Monthly Report. The height of this station is 1823 
feet above sea-level. These two almost contiguous 
stations, the higher being on a peak and the lower also 
on an eminence sloping directly down to the sea, form an 
admirable pair of stations for furnishing, in the best pro- 
curable form, the observational data necessary for some 
of the more important physical inquiries of meteorology. 
So far as we are aware, no pair of stations can be placed 
side by side with Hong Kong Observatory and Victoria 
Peak as affording the data for the physical inquiries re- 
ferred to, except Ben Nevis Observatory and the station 
at Fort William. 
Of these inquiries the important practical question of 
the rate of decrease of temperature with height may be 
cited as an example. The remarkable suitability of these 
two groups of stations for advancing this inquiry lies in 
the circumstance that in each case the upper station is 
situated on a true peak, thus reducing to a minimum the 
influence of the land in changing the temperature of the 
winds before arriving at the Observatory ; and that the 
lower station is on a rising ground near the sea and 
sloping down to it, thus minimising the disturbing effects 
of radiation. At Hong Kong the rate of decrease of 
temperature with height is 1° for 261 feet in winter ; 347 
feet in spring ; 262 feet in summer; 254 feet in autumn ; 
and 281 feet for the year. At Ben Nevis the rates are for 
the seasons 279, 251, 268, and 290 feet, and for the year 
270 feet--the results being thus closely accordant. On 
the other hand, such a pair of stations as Obirgipfel in 
Austria, on a peak 6706 feet high, and the neighbouring 
station at Klagenfurt, 1437 feet high, cannot furnish the 
data necessary to this inquiry owing to the circumstance 
that the lower station is situated in a deep valley. The 
result is that in January the difference of the mean tem- 
peratures of the two stations is less than 1°, although the 
one is 5269 feet higher than the other ; whereas in May 
the difference of their mean temperatures is 220. 
It is earnestly hoped that the publication z# extenso of 
the hourly observations at Hong Kong will not be limited 
to ten years, as seems to be hinted at in the Report, but 
that the meteorological observations and their publi- 
cation will be made a permanent part of the work of the 
Observatory. The unique position of Hong Kong with 
respect to the great continent of Asia and its meteorology 
will no doubt secure this object. 
CHOLERA IN ITS RELATION TO WATER- 
POA AVEN A 
pee epidemic of Asiatic cholera, which has been 
raging in Spain during the last two years, and which 
appears even yet to be lurking in some portions of that 
peninsula, has furnished some interesting data as regards 
its connection with water-supply, to which it would be 
wise in us to direct our attention, not only from the inter- 
esting nature of the facts as such, but also because it is 
not improbable that ere the disease quits Europe it may 
visit our own shores. 
Broadly speaking, it would appear that in Spain this 
formidable disease never became truly epidemic or dan- 
gerous in any city in which there was a pure and good 
supply of water, and proper means were taken to guard 
against the sources being polluted by any of the specific 
choleraic poison. 
In support of this idea I would desire to call attention 
to the cities of Toledo, Seville, Malaga, and Madrid, in 
contradistinction to such places as Aranjuez, Saragossa, 
Granada, and Valencia. I will commence with Madrid. 
