154 THE FAUNA OF THE SALCOMBE ESTUARY. 



eastward, so that its waters become more sheltered from the southerly 

 weather. At its north-eastern end are two large but shallow creeks, 

 which at low tide become large mud-flats, with only a small stream 

 running through each — Batson Lake and Southpool Lake — as well as 

 the narrow entrance to the Kingsbridge estuary between Pilworthy 

 Point and Snape's Point. 



The Kingsbridge estuary, as is usual in these cases, has a deep 

 winding channel, which is bounded on either side by large mud-banks 

 covered with water only at high tide. A number of creeks with similar 

 extensive mud-banks run into the main estuary, and there is situated 

 at some distance from its mouth an island known as the Salstone, 

 which at high tide is quite submerged. 



The Nature of the Water. — Compared with the size of the whole 

 estuary and the volume of sea-water which enters with the tide, the 

 various streams which run into it are small, and the amount of fresh 

 water which enters the estuary is not sufficient to seriously reduce 

 the density. In Salcombe Harbour proper, and probably in the Kings- 

 bridge estuary as far up as the Salstone, the density of the water, 

 excepting in times of flood, is very nearly that of Channel water. The 

 following observations of density were made by Mr. Garstang from the 

 Dawn, which was moored off Ditch End, at the north-east end of 

 Salcombe Harbour: — 



Aug. 7th, 1900 (low water 8.30 p.m., 12 ft. 7 in. tide), 7.45 p.m. ; 



temperature of water, 17° C; density at that temperature, 1'026. 

 Aug. 8th, 1900 (high water at 3.12 p.m.), 2.30 p.m. ; temperature of 



water, 15-6° C; density, 1-0267 at 16° C. 



A third determination was made by Mr. Todd between Garston Point 

 and the Salstone in the upper part of the Kingsbridge estuary, and gave 

 the following : — 



Oct. 10th, 1900 (low water 12.49 p.m., 16 ft. 8 in. tide), 12.45 p.m.; 

 temperature of water, 157° C. ; density at that temperature, 1'0266. 



Temperature. — Owing to the extensive area of the mud-flats, which 

 are covered by the rising tide with a shallow layer of water, the water 

 in the estuary must necessarily be subjected to considerable changes 

 in temperature, which will vary in direction and magnitude according 

 to the season of the year. To these changes of temperature, which 

 will often be very sudden, the animals living in the estuary must 

 of necessity be adapted. 



The Movements of the Water. 1. The Tides. — The tidal current in 

 Salcombe Harbour is exceedingly strong, and the scour, especially at 

 spring tides, is very considerable in the centre of the stream. The 

 maximum rise and fall is about 17 ft. 



