210 CORAL AND ATOLLS 



prolonged periods in which the lagoon is almost unrippled,and 

 even the windward islands are almost deserted by the breeze. 

 The high annual rainfall of 70'23 inches gives rise to the 

 curious phenomenon of the fresh-water wells in which water fit 

 for drinking rises and falls with the movements of the tide. On 

 Pulu Tikus no fresh water may be found in wells, and though, 

 in the more rainy months, fresh water is to be found at a depth 

 of a foot or so below the surface of the land, it soon becomes 

 brackish, and finally entirely salt ; long rainless spells therefore 

 occasion great inconvenience, and the island vegetation soon 

 becomes parched in the hotter part of the year. It is the 

 presence of so much rain that prevents the accumulation of 

 guano on the bird-covered Keeling Island, and it is the rain 

 that, carrying the droppings in a state of solution through the 

 permeable coral, causes the deposition of the phosphates which 

 occur in the upper layers of the soil of Cocos-Keeling, and 

 which have made Christmas Island of so great a commercial 

 importance. 



From time to time in the history of the islands long rain- 

 less spells have occurred, and during 70 consecutive days at 

 the end of 1905 only -37 of an inch fell ; and this very small 

 quantity was distributed over nine separate showers. During 

 the whole of these dry periods rain- clouds are for ever 

 coming up and passing by the islands, and it has long been 

 noticed here that a rain mass will divide before reaching the 

 coral ring, and part pass away to the south and part to the 

 north. This is an interesting fact and is of such common 

 occurrence that an explanation must be readily to hand ; and 

 it is doubtless this, that the overheated coral, which in the sun- 

 light dances and quivers with a dazzling whiteness, gives rise to 

 such a column of heated air that the upward-rushing mass is 

 sufiicient to cut the oncoming rain-cloud into two parts. This 

 is the explanation, I have since learned, that was also furnished 

 by Mr. J. D. Hague to account for a similar state of things in 

 Jarvis Island. Quite apart from rain-storms, clouds may be 

 often seen to melt away as they come over the group, be- 

 coming thinner and thinner as they meet the hot air and 



