64 CHALLENGER 



until they meet the land, when they are deflected to the right 

 in the northern hemisphere and to the left in the southern hemi- 

 sphere, setting up great clockwise current movements in the 

 North Atlantic and North Pacific, and anti-clockwise movements 

 in the South Atlantic, South Pacific and Indian Ocean. These 

 movements carry cold water along the eastern sides of the three 

 great oceans towards the equator to take the place of the west- 

 ward-flowing water, and this does much to account for the lack 

 of coral growth in these regions, for the coral polyp does not 

 endure in a temperature of less than 2o°C. 



The coral polyp, which must be regarded as a sea anemone 

 which lives and multiplies by extracting lime from sea water, 

 thrives therefore in the western parts of the great oceans, between 

 the latitudes 30 North and 30 South, where the water is warm 

 enough for its tastes. 



The coral reefs, which are built up of the countless calcareous 

 skeletons of coral polyps, will often build out more readily to 

 windward of an island where abundant 'food' is brought by the 

 water of the west-flowing current. Thus in the Grenadines great 

 areas of reefs grow out to the eastward, leaving behind them bays 

 and passages between themselves and the land; whereas on the 

 western side of the islands there are practically no reefs. 



The Trade Winds were blowing strongly on to the reef-fringed 

 eastern side of the Grenadines in May and June, and no inshore 

 work was possible in this area until the winds eased off about the 

 middle of August. As soon as this happened, work on the western 

 side of the islands was suspended, a camp was established at Little 

 St. Vincent, and both the sounding boats concentrated on the 

 weather side of the reefs during a spell of calmer weather. 



So the survey went on, the Captain constantly thinking ahead 

 and planning to make the most of changing weather conditions, 

 his First Lieutenant putting his plans into practice, arranging for 

 men to go into camp, for stores and fuel to be landed, while the 

 Engineer Officer seized every opportunity to carry out mainten- 

 ance work on his boats, which ceased running only for a few hours 

 at the week-ends. 



In June, the Captain was promoted in the Half-Yearly Pro- 

 motions to Commander, and after the customary celebrations 



