Ch. V. OF COKAL-REEFS. 143 



sidence, would sometimes become dissevered into 

 smaller ones. In the Marshall and Caroline Archipela- 

 goes, there are atolls standing close together which 

 have an evident relationship in form ; and we may sup- 

 pose that either two or more encircled islands originally 

 stood close together and afforded bases for two or more 

 atolls, or that one large atoll has been dissevered. But 

 from the position as well as the forms of three atolls 

 in the Caroline Archipelago (the Namourrek and ElatO' 

 groups), which are placed in an irregular circle, I am 

 strongly inclined to believe that they owe their origin 

 to the disseverment of a single large atoll. 1 



Irregularly-formed Atolls, — In the Marshall group, 

 Musquillo atoll consists of two loops united by a single- 

 point ; and Menchicoff atoll is formed of three loops, 

 two of which (as may be seen in fig. 3, Plate II.) are- 

 connected by a mere ribbon-shaped reef; the three 

 together being 60 miles in length. In the Gilbert group 

 some of the atolls have narrow reefs like spurs, project- 

 ing from them. Linear and straight, or crescent-formed 

 reefs with their extremities more or less curled in- 

 wards, may sometimes be found standing by themselves 

 in the open ocean. All these irregular forms would 



1 The same remark is, perhaps, applicable to the islands of Ollap, 

 Fanadik, and Tamatam in the Caroline Archipelago, of which charts- 

 are given in the atlas of Duperrey's voyage ; a line drawn through the 

 linear reefs and lagoons of these three islands form a semicircle- 

 Consult also the atlas of Lutke's voyage ; and for the Marshall group 

 that of Kotzebue ; for the Gilbert group (which is referred to in the- 

 ensuing page) consult the atlas of Duperrey's voyage. Most of the- 

 points here referred to may, however, be seen in Krusenstern's general 

 Atlas of the Pacific. 



