THE BURE AND ITS TRIBUTARIES. 
253 
have seen above, Mr. Sutton regards it as improbable that the 
Broad water could have derived this amount of salt from the 
atmosphere. 
In this connection we are indebted to Mr. Rising for the 
following note : — “ The higher salinity of the Broads near the 
sea is also attributed by chemists to the prevalence, at times, 
of dense sea fogs, which cling to the reed beds and leave a salt 
deposit.” There can be little doubt that all the salt deposited 
out of the sea fogs on an extensive tract of reed-grown marsh 
land finds its way into the Broad owing to the action of rain. 
Taking this into consideration the observed salinity might 
certainly be accounted for in this way. Mr. Rising continues : 
— “ Horsey Mere is also fed by drainage mills which pump the 
water from a large area of marsh land formerly inundated by 
the sea, and no doubt impregnated with saline matter.” It 
is worthy of note that the Broads near the sea like Horsey 
Mere have a higher salinity than Broads further inland like 
Hickling. Barton Broad, still further away from the sea, has 
a slightly higher salinity than the waters of the Ant imme- 
diately above it, due no doubt to the same influences which 
cause the high salinity of the Broads of the Hickling group. 
These influences are thus at work over an area which includes 
both the Broads of the Thurne River, and Barton Broad on 
the Ant, but their effects become much less marked as one 
proceeds inland from the coast. This could be explained by 
the theory of “ percolation through the sub-soil,” but it 
agrees quite as well with the “ sea fog ” theory. A final 
decision on the point seems hardly possible on such data as 
are at present available. 
The salt found in the Thurne River having thus been traced 
to its source in the Broads of the Hickling group, it only 
remains to explain the steady fall in salinity as the river is 
descended. Two causes contribute to this ; first, the dilution 
of the salt water by the numerous dikes and mills which 
discharge fresh water into it, and, secondly, the entry of fresh 
water from the Thurne Mouth to Acle stretch of the Bure, 
which water has already been shown to be pushed up by the 
rising tide, and which divides itself at Thurne Mouth, one 
