530 N'OTES OX THE PHYSICAL CONDITIONS EXISTING 



is fully exposed to the southerly and westerly gales, but sheltered from 

 the easterly. Conversely, the arm which extends out to the Start is 

 sheltered from the westerly gales, and only the easterly and south- 

 easterly winds affect it strongly. 



It has long been known as a good fishing-ground, and at the present 

 day from seventy to eighty of the Brixham boats trawl over it regularly 

 throughout the year. From the point of view of the fisheries this 

 area is of great interest, for it displays within comparatively narrow 

 limits all the important biological problems in connection with the life 

 histories of food-fishes, as well as the physical conditions with which 

 those life histories are so closely related. 



Tides and Currents. 



The movements of the tides in the EngUsh Channel are complicated 

 by the numerous bays and inlets of the French and English coasts. 

 In the centre of the Channel the periodic ebb and flow is fairly regular, 

 but even there the cross currents caused by in-draughts into the 

 various bays on both coasts produce a rotary motion at the changes 

 of the tides, which is only approximately constant as regards direction 

 and duration. Without entering too far into the details which may 

 be found in Channel pilot books, the tidal currents and their strengths 

 may be referred to so far as they concern the Great West Bay. 



The Channel is divided into three main regions : the first lies to the 

 west of the Lizard in Cornwall ; the second from the Lizard to Start 

 Point; and the third from Start Point to Beachy Head. In the first 

 division the state of the tides is always the reverse of that in the third, 

 i.e. with regard tx) ebb and flood ; in the second region it is "intermediate," 

 agreeing for one half of the tidal period with the outside main tidal 

 stream, and for the other half with the " true Channel stream " between 

 Start Point and Beachy Head. There is no definite line of demarcation, 

 however ; what happens is that whilst the " true Channel stream " is 

 flowing, the condition intermediate between ebb and flood, i.e. slack 

 water, is gradually passing from the Lizard to the Start until it reaches 

 the latter point two hours before high water at Dover. To the west of 

 Start Point, therefore, the ebb is going to the west for one hour whilst 

 the flood to the east of Start Point is still travelling to the east. The 

 " true Channel stream," as is well known, suddenly changes after high 

 water at Dover throughout the third region and ebbs to the west. For 

 the short space of one hour the direction of the tidal current is the 

 same throughout the entire Channel, i.e. to the west, then the flood 

 begins to make at the western end, and for the next four hours the 

 second region is the centre of opposing forces. In the western end of 



