26o 
MR. A. G. INNES ON TIDAL ACTION IN 
of the river. Mention of this circumstance has already 
been made during the discussion of the abnormally high 
salinity of the Broads of the Hickling group. As was there 
observed, it is probable that Barton Broad derives its extra 
salt either from a percolation of sea water through the sub- 
soil of the Broad, or from the salt deposited on the reeds 
out of the sea fogs. A definite decision between the two 
alternatives is scarcely justifiable without further data than 
are at present available. In view of the greater distance of 
Barton Broad from the coast it is natural that the increase 
in salinity should be less pronounced than it is at Hickling. 
The possibility that salt water (from the Thurne River) 
should be “ backed up ” the Ant into Barton Broad is 
negatived by the fact that the salinity of the Bure at Ant 
mouth is lower than it is in the lower portion of the Ant 
itself (see Table XI.), so that any water so “backed up’’ 
would lower the salinity instead of raising it. 
Some attempt was made to examine the distribution of salt 
in Barton Broad (Table X.). The result shows that the 
salinity is not quite uniform throughout the Broad (Hickling 
Broad is also irregular in this respect). No one part of the 
Broad can, however, be pointed to as the source of the salt. 
The Ant is thus a normal fresh-water river, and it appears 
to be beyond the reach of the secondary “ backing-up ” action 
of the tide in the Bure. 
Barton Broad contains traces of salt derived either from 
the sub-soil, or from the salt left on the reeds by the sea fogs. 
This salt also raises to a small extent the salinity of the River 
Ant below Barton Broad. 
SECTION VI. 
Abnormal Tides. 
All the regularities and relationships noticed in the preceding 
sections are occasionally upset by the occurrence at Yarmouth 
of abnormally high tides. Though these are quite rare their 
effects are interesting, and, as one such tide occurred in 1906, 
