158 DISTRIBUTION OF CORAL-REEFS. Ch. VI. 



a moderate distance from it where the bottom is 

 gently inclined ; but they never include a deep-water 

 moat or lagoon-like channel running parallel to the 

 shore. It must, however, be remembered that fringing- 

 reefs are frequently breached by deep-water channels, 

 where mud has been deposited in front of rivers and 

 valleys. 



In all cases, a space of 30 miles in width has 

 been coloured round or in front of the reefs of each 

 class, in order that the colours might be made con- 

 spicuous in a map on so small a scale. 



The vermilion spots and streaks represent vol- 

 canos now in action, or historically known to have 

 been so. They are laid down chiefly from Von Buch's 

 work on the Canary Islands; and my reasons for 

 making a few alterations are given in the note below. 1 



1 I have also made considerable use of the geological part of Berg- 

 haus' Physical Atlas. Beginning at the eastern side of the Pacific, I 

 have added to the number of the volcanos in the southern part of the 

 Cordillera, and have coloured Juan Pernandez according to observations 

 collected during the voyage of the Beagle (Geol. Trans, vol. v. p. 601). 

 I have added a volcano to Albemarle Island, one of the Galapagos 

 Archipelago (see my Journal of Kesearches, p. 457). In the Sandwich 

 group there are no active volcanos, except at Hawaii ; but the Rev. W. 

 Ellis informs me there are streams of lava apparently modern on 

 Maui, having a very recent appearance, which can be traced to the 

 craters whence they flowed. The same gentleman informs me that 

 there is no reason to believe that any active volcano exists in the 

 Society Archipelago ; nor are there any known in the Samoa or Navi- 

 gator group, although some of the streams of lava and craters there 

 appear recent. In the Friendly group, the Eev. J. "Williams says (Nar- 

 rative of Missionary Enterprise, p. 29) that Toofoa and Proby Islands 

 are active volcanos. I infer from Hamilton's Voyage in the Pandora 

 (p. 95), that Proby Island is synonymous with Onouafou, but I have not 

 ventured to colour it. There can be no doubt respecting Toofoa ; and 



