62 EEPORT OF THE COUNCIL. 



Section II.— HYDROGRAPHIC AND PLANKTON WORK 

 IN THE ENGLISH CHANNEL. 



The Hydrographic programme of previous years has been carried 

 out on the quarterly cruises in the English Channel, and the results up 

 to the end of September 1906 have been published in the Bulletin, 

 The work has been rendered unusually difficult by bad weather, and 

 only one set of current measurements has been made. Severe gales 

 made it impossible to complete the November cruise, and the three 

 stations to the east of the Isle of Wight were omitted. The area is 

 to a certain extent covered by the lines of samples taken by steamers 

 sailing from Southampton and Newhaven. 



Fortnightly samples and observations of Surface Temperature have 

 been received from the captains of steamers crossing the English 

 Channel, and from five lightships. Outside the English Channel, 

 regular samples have also been received from the captains of liners, 

 covering the North Atlantic south of 56° N. latitude. 



The salinity of the English Channel has been slowly decreasing 

 during the past year, the decrease beginning in the western half 

 which is influenced by the southerly flow of fresher water from the 

 Irish Sea. This flow was well marked during February, but no 

 division into layers of different salinity was found at any of the 

 stations. In the eastern half of the Channel the change did not com- 

 mence till three months later, water of 3 5 "4 7oo S. being still 

 found on the Newhaven-Caen line during the latter half of April. 



The decrease in salinity referred to in a previous report has 

 continued. 



In May 1906 there was a very decided fall over the whole of the 

 English Channel. The salinity at Station 3, oft' Ushant, increased 

 fairly regularly with the depth, being 35'21 7oo ^^ the surface and 

 35"34 7oo ^^ 110 metres. This difterence is apparently due to the 

 coastal water of Brittany, and is not connected with the sharp 

 division into layers that is sometimes found on the more westerly 

 stations. At all other stations during May the water was homo- 

 geneous from top to bottom. 



During the two following months the decrease of salinity still con- 

 tinued, and no value as high as 35 7oo ^^^^ found on the Newhaven- 

 Caen line during the latter part of July. 



The August cruise showed a strong southerly flow from the Irish 

 Sea across the western entrance to the Channel and a decided division 

 into layers of different salinity on all the western stations except the 

 one oft" Ushant. The diflerences between the surface and bottom 

 salinities were greatest on the more northerly positions, especially off" 



