ECOLOGY OF THE MURRAY ISLAND CORAL REEF. 5 



western side this crater rim rises to a height of about 750 feet, but on the 

 southeastern side it is only about 250 feet high. Hedley believes that the 

 greater height of the westerly part of the crater rim is due to the southeast 

 trade winds, which for about eight months in the year blow steadily across 

 the island and would thus drift any ejected dust and ashes in a northwesterly 

 direction. F. A. Potts, however, doubts the sufficiency of this simple expla- 

 nation and presents evidence tending to show that the peculiar shape of the 

 crater rim may be the result of one or more explosions. Within this chief 

 crater of the island, situated somewhat eccentrically near the southeast 

 side, there is a smaller and more recent ash-crater, at present consisting of 

 two conical hills, the highest of which rises about 400 feet above sea-level and 

 250 feet above the floor of the great crater. 



Fig. 2. — View of Maer Island looking northward from the summit of Wyer Island. Traced from a 



photograph taken by A. G. Mayer. 



An extensive flow of lava proceeded from this smaller crater and broke 

 through the northeast side, forming a large, oval, tongue-shaped projection 

 which constitutes the northeasterly half of the island and is now covered with 

 a dense growth of cocoanuts and other trees. (See plate 3 b.) Indeed, one 

 may readily distinguish at a distance between the regions of ash-deposits 

 and lava-flow, the former being almost barren save for a tangle of coarse 

 grass and the lava being thickly covered with palms and other trees. More- 

 over, the decomposed ash is dull gray-brown and the lava rich reddish-brown. 



Three streams, which flow only during the rainy season, have cut deep 

 ravines into the slopes of the island. The largest of these we call Bruce 

 Brook, in honor of John Bruce, esq., the well-known anthropologist, who as 

 teacher and resident magistrate of the island has for more than twenty years 

 labored to improve the condition of the natives. Bruce Brook flows out 

 from near the center of the principal crater in a general northeasterly direc- 

 tion, making its way first over the floor of the crater and lower down over 

 the region between the ash-rim and the lava-flow, cutting deeply into the 

 underlying ash and forming cascades over the superficial lava. Another 

 water-course, which we call Hedley Brook, in honor of Charles Hedley, well 



