THE BURE AND ITS TRIBUTARIES. 249 
junction with the Thurne River, thus temporarily reversing 
its ordinary direction of flow. The River, above Acle, can 
therefore only be called “ tidal ” in a restricted sense. The 
term “ Tidal river ” appears capable of various interpretations. 
According to one witness in the Great Yarmouth Waterworks 
Case (Minutes of Evidence, House of Lords, 26th June, 1906, 
p. 12), “ Fresh water is frequently tidal, and it is tidal here. 
It may be, as in some of the great lakes in America, for 
instance, tidal owing to the moon’s action, as it is in the sea, 
although perfectly fresh ; or it may be, as here, tidal owing 
to the salt water coming into the lower reaches and holding 
up and pushing back the water in the higher reaches.” 
The essential feature of “ tidal action ” would seem to be 
that the rise and fall should be regular, and corresponding 
in period to the rise and fall in the ocean. 
Summarising the above conclusions, the tidal action in 
the Bure below Thurne Mouth is a two-fold one. It consists 
firstly in an ebb and flow of salt water, the presence of which 
can be detected in the river as far up as Acle, but no further. 
Secondly, there is, above Acle, the backing up of fresh water 
already described. 
SECTION III. 
The Thurne River. 
Table III. shows the salinity of the waters of the Thurne 
River from the mouth up to Candle Dike, and thence 
through Deep Dike, Whitesley and Hickling Broad. The 
samples were collected on upward and downward journeys 
made on September 12th, 1906. On the same day a journey 
was made up Meadow Dike to Horsey Mere, and the analyses 
of the samples obtained are recorded in the same table. 
The results show that on entering the Thurne River one 
finds a rapid rise in salinity to about 29 grains of Chlorine per 
gallon, or roughly twice the amount found in the Bure below 
the confluence. 
