510 MR. W. G. CLARKE ON THE MERES OF WRETHAM HEATH. 
level of saturation in the Chalk. The height above sea-level of 
the beds of these meres is apparently about the same. To the east 
of Ringmere the road is 106 feet above sea-level; the “Drove” 
immediately south of Langmere is 110 feet above sea-level, the 
track rising to 137J feet at the plantation about mid-way between 
Langmere and Fowlmere. Nearer the latter mere a height of 140 
feet is attained, dropping at the southern end of the mere to 
120'8 feet. Taking the years 1859 and 1862, one or both of 
which were dry years so far as the meres are concerned, 1882 
which was a full year, and 1902, which was a dry year, and com- 
paring the Norfolk rainfall for periods of five and ten years pre- 
ceding, we get the following data: In the ten years from 1872 to 
1881, inclusive, the rainfall was 277"62 inches; from 1849 to 1858, 
224 - 33 inches; and from 1852 to 1861, 226'04 inches; while 
from 1892 to 1901, inclusive, the rainfall was 243 61 inches. 
Between the ten-year dry periods and the ten-year wet periods 
there is thus a maximum difference of fifty-three inches or 5 '3 per 
year, and a minimum difference of thirty-four inches or 3 - 4 per 
year. In the five years preceding the full meres of 1882 and the 
dry meres of 1862 and 1902 the figures show a far greater diver- 
gence. The rainfall from 1854 to 1859, inclusive, was 102-31 
inches; and from 1857 to 1861, inclusive, 112-18 inches; from 
1897 to 1901, inclusive, 117 "39 inches; while in the wet period of 
1877 to 1881, inclusive, the rainfall was 149 69 inches. This 
shows a maximum difference in the quinquennial periods of forty- 
seven inches or 9 -4 per year and a minimum of thirty inches or 
six per year. This seems quite sufficient to account for the 
remarkable fluctuations of the water in these meres, while the fact 
that in the intervening periods one mere is sometimes high while 
at the same time another close by is low, may perhaps be due to 
the slight differences in level. For instance, if the saturation level 
were eighteen feet beneath the ordinary surface, a mere whose bed 
was nineteen feet from the surface would contain a foot of water 
when one whose bed was seventeen feet from the surface would be 
quite dry. It may also be noted that in 1882 when the meres 
were at their highest level for many years, the rainfall was 33‘34 
inches, the highest yearly register for many decades. 
Reasoning from previous experience it may therefore be 
