The Sun.
London, England, 1868-08-25 00:00:00

MATHEMATICAL AND PHYSICAL SCIENCII

SECTION.

The results of the labours of the Rainfall Committee
were communicated to this section by Mr. G. Y. SYMONS,
the secretary, who stated that the extraction and classifi-
cation of all trustworthy records of rainfall, whether
published or unpublished, was kept prominently in view,
and steadily pursued on every opportunity, as was also the
examination of rain-gauges in situ by the secretary, who
travelled about the British Isles during portions of each
year in order to ascertain that the rain-gauges used by the
observers now assisting (about 1,600 in number) were
accurately constructed instruments, and were placed
in suitable positions. Mr, Symons referred briefly
to the fact that in a voluntary body of observers
such as that now recording the rainfall through the
length and breadth of the land, removals and deaths
would occasionally leave small districts unrepresented,
and, as in parts: of Derbyshire, Wales, Scotland, and
Ireland other parts had never been adequately provided.
From these causes additional observers were at all times
most welcome, but they must conform to the rules of their
confrere., so as to secure uniform. results. The Secretary
then referred to certain expniments which were suggested
some few years since relative to the effects which would
result from inclining the funnels of gauges towards the
rain ; not, of course, with the remotest idea of any
but horizontal gauges being ever used for any but experi-
mental purposes. Tables were presented illustrating the
results of these instruments, for the construction and
observation of which the country was indebted to Mr.
Chrimes, of Rotherham. Their discussion proved the
following facts :-1. That there was no month in the year
in which a gauge whose mouth is horizontal collected so
much as one which was kept face to the wind by a vane.
2. In summer rain fell nearly vertical, the average angle
then being about 20 deg., in spring and autumn 46 deg.,
and in winter more than 60 deg. 3. The ratio of the fall
on the ground to that at 25ft. above it, bore a nearly
constant relation to the angle of fall ; for in-
stance, in two months, when rain fell at a
mean angle of 65 deg. from the vertical the
25ft. gauge collected 25 per cent. less than that on the
ground ; and, on the other hand, in two months when the
mean an,gle was 20 deg., the upuer and lower gauges only
differed by 5 per cent. Reference was then made to the
removal of various experimental gauges from Caine to the
vicinity of Reading, and to the rainfall of parts of Cumber-
land and Westmoreland, one point specially deserving of
notice being that, by independent and different modes of
inquiry, Professor Phillips and Mr. Symons had arrived at
very similar results as to the height at which the greatest
amount was usually to be found—the former giving 1,463
feet, and the latter 1,000 to 1,500 feet. Considerable space
in the communication was devoted to the determination of
the relative wetness of different months based on the
average of many years ; and it was shewn that the greater
the total fall in the year the more certain was
it that the wettest month would he a winter one,
whereas in dry districts like Norwich the wettest
month was in summer or early autumn. A very
complicated investigation was next mentioned relative to
variations in the percentage of decrease of rain due to
elevation above the ground in different months, of which
it may be briefly said that the result appeared to be that
while a gauge on the roof in every month collected less
than one on the ground, the decrease was much greater in
winter than in summer, and upon the values in the tables
various correction factors were based. Remarks on the
rainfall of the last two years concluded Mr, Symons's
coMAlU.OicartiOuf ._ -