THE WEST INDIES 63 



rum, that they had added some small contribution of their own 

 to the vast whole of the world's maps. 



Every day the ship and the boats were slowly covering the sea 

 with lines of soundings. Backwards and forwards they went, first 

 running in towards the shore, then to seaward again; the boats 

 worked along the coast in the shallower water of less than ten 

 fathoms or so, the ship carrying on the sounding to seaward of 

 the boat's limits. The sextant and station pointer method of fixing 

 is used in such cases but as the boats and the ship are moving an 

 officer and a recorder take the two horizontal angles simulta- 

 neously at the word 'Fix', which is heard at frequent and regular 



Three fixed marks 

 used for fixing 



Angle taken 



second observer 



Theory of station pointer fixing 



intervals throughout every long day's sounding. The lines along 

 which it is proposed to sound are drawn on the field-board, and 

 by steering the appropriate course, and by making small altera- 

 tions whenever a fix shows that the ship or boat is being set off 

 the line, an endeavour is made to follow the planned lines which 

 will give a regular sounding coverage of the area. 



Ocean currents are caused by the friction of wind upon the 

 surface of the sea, and the North-East and South-East Trade Winds 

 set up westerly-moving currents north and south of the equator 

 respectively. These great equatorial currents continue westwards 



