CORAL REEFS. APPENDIX. 221 



thicknesses of coral-made rock, whether formed in the one way 

 or the other, have heen removed from the elevated reefs of the 

 Solomon Islands, wherein lies the evidence that there has been 

 no subsidence? 



H. B. Guppy. " The Solomon Islands." 1887. 



" The Coral-Reefs of the Solomon Islands." Nature, Nov. 

 25, 1886. 



" Observations on the Recent Calcareous Formations of the 

 Solomon Group made during 1882-84." 



The principal facts contained in these papers bearing upon 

 the coral-reef problem have been considered in the preceding 

 review of Mr. Guppy's paper " Notes on the Characters and 

 Mode of Formation of the Coral Reefs of the Solomon Islands." 



W. J. L. Wharton. " Masiimarhu Island." Nature, Pep. 1, 1888. 



A delineation of two slopes of the coral reef surrounding the 

 small island of Masamarhu (situated in the Red Sea, in Lat. 

 18° 49' N. and Long. 38° 45' E.), as determined by Captain 

 Maclear, of H. M. S. " Flying Fish." This is an important 

 contribution to the history of reef-structures, since it places 

 beyond doubt the fact that the seaward slope of some coral 

 islands is very abrupt, as earlier determinations had reported. 

 At one point removed about 375 feet from the growing edge of 

 the reef soundings indicated a depth of 1200 feet, or an aver- 

 age descent for this portion of the slope of some 72°. At a 

 distance of 1200 feet the depth was found to be 1300 feet. 

 Beyond this point the seaward slope is somewhat less abrupt, 

 and at a distance of about 1900 feet a depth of -'only 1500 feet 

 was found. Even this is a steep slope, averaging 38°, and 

 fully equal to the slope of the steeper volcanic cones ; the first 

 portion of the descent, on the other hand, far exceeds the slope 

 of any mountain-peak with which we are acquainted, except 

 where sheer (so-called " vertical ") rock-precipices are presented. 

 Coral and coral sand were obtained from nearly all parts of 

 the slope, and at one point coral limestone was struck at 1300 

 feet. In two or three places the line dropped into deep and 



