ON THE RAINFALL IN THE BRITISH ISLES. 435 
ciety, and seems to us of such importance that we have transferred it to the 
Appendix to this Report. Professor Phillips found that in the Scawfell group 
the maximum fall was at an altitude of 1463 feet; Mr. Symons*, by an 
entirely different method, had determined that the maximum was at an alti- 
tude of 1000 to 1500 feet; the two methods, therefore, have led to some- 
what similar results. 
The examination of rain-gauges has been continued as opportunity offered, 
and on exactly the same plan as previously, except that a small instrument 
termed an “ altameter” has been designed by Mr. Symons for his own use 
in determining the angle of elevation of trees, buildings, &c. above rain- 
gauges, and therefrom the suitability of the position in which the gauge may 
have been placed. ‘It consists of a brass tube 6 inches long Fig. 3. 
and three-quarters of aninch in diameter; near the top are == 
double gimbals (c), by the outermost of which the instrument 
is suspended between the fingers, when, of course, the body 
assumes a truly vertical position. At the lower end is a 
small mirror (p), turning on a horizontal axle, whereof one 
end is prolonged at ©, and carries a pointer on the graduated 
are (AB). If the mirror is (as represented) at an angle of 45°, 
objects level with the mirror will be seen in its middle, by 
looking through the small eye-hole at the top ; but if objects 
are above its level, the mirror must be turned by the axle 
() into a more horizontal position ; and when the objects are 
seen crossing the centre of the mirror, the index will be found 
as many degrees towards a as the objects are above the instru- 
ment.” 
In our last Report to this Association, attention was drawn 
briefly to the variations in the proportion of the mean an- 
nual rainfall which is measured in the different calendar 
months ; and a Table was given, from which it appeared that, 
at stations south of the Tweed, the principal part of the 
rainfall occurs in summer where the total fall is small, and 
in winter where it is large. But the data used in preparing that Table ex- 
tended over a pericd of only ten years; a hope was therefore expressed that 
during the ensuing year a full investigation might be made, and some further 
light thrown on the subject. 
This has now to some extent been done—though, as in all meteorological 
investigations, the further search has discovered fresh difficulties and com- 
plications, many of which must stand over for future discussion. The follow- 
ing, however, is a brief account of the steps which have been taken, and the 
results attained since the last Report. 
The mean annual and monthly rainfall for all available stations in each 
decennial period since the year 1730 were first calculated and tabulated, the 
stations being arranged alphabetically for easy reference; this involved the 
extraction of nearly 40,000 monthly readings. From these figures the values 
for monthly percentage of the annual fall were calculated + and tabulated in 
a similar manner, together with the actual mean annual fall for each station 
during each decennial period. 
As the Table given last year seemed to show that the time of the 
maximum monthly fall varies with the total amount registered in the year, 
* British Rainfall, 1867. 
t By F. Gaster, Esq., F.M.S., who has also drawn up the following abstract of the re- 
sults he has obtained. 
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