566 W. M. DAVIS SUBSIDENCE OF REEF-ENCIRCLED ISLANDS 



that the experts to whom the material was submitted should publish de- 

 scriptions of the material, but should draw no conclusions from the facts 

 as to the mode of formation of the atoll. The writer believes that he is 

 correct in stating that these exj^erts were unanimous in their views that 

 the published descriptions supported Darwin's subsidence theory, and in 

 fact were fairly susceptible of no other known explanation" (1918, a, 86). 

 It is also very properly pointed out that "if any part of the bore repre- 

 sented material fallen from above,'' as must have been the case had the 

 atoll been formed by outward growth on its own talus, according to Mur- 

 ray's theor)", "an admixture of shallow and deep water forms must have 

 occurred. Not a trace of deep-water forms was found in the lower or in 

 any other part of the Funafuti bore" (88). The organisms found in the 

 bore are still flourishing in the surface reef or in the lagoon. Skeats' 

 argument for subsidence, based on the dolomitization of reef limestones 

 (1918, 6), deserves special attention. In view of all this, it seems fully 

 warranted to regard Funafuti as having been formed by upgrowth during 

 the slow subsidence of its foundation, and therefore as confirming Dar- 

 win's theory. 



THE BERMUDA BORING 



A deep boring in Bermuda was reported upon four years ago by Pirsson. 

 It penetrated the island to a depth of 1,1:13 feet from a point 135 feet 

 above scale vel. The first 380 feet were in limestone ; fragmental volcanic 

 material, much altered, as if by subaerial oxidation, was then encoun- 

 tered 245 feet below sealevel, and continued for 210 feet; this was fol- 

 lowed by 105 feet of water-worn volcanic sand and gravel; then at a depth 

 of 560 feet below sealevel solid lava began and continued to the bottom, 

 except that "a bed of [volcanic] sand . . . which had been Avorn 

 upon a beach" (1914, 197) was passed through from 910 to 940 feet below 

 sealevel, or more than 300 feet below the solid volcanic rock. It is in- 

 ferred that "Bermuda was once an island, composed of volcanic rocks 

 rising above the level of the sea, which has been entirely cut away by the 

 action of the waves" (199) ; the island is represented in a diagTam evenly 

 truncated at the depth at which the weathered fragmental volcanic rock 

 was first reached. "The present depth of water over the different [trun- 

 cated] banks and the extent to which the bore penetrates before passing 

 through the limestones into water-worn debris seems to indicate a change 

 in water level of perhaps 200 feet since the time when the waves were 

 attacking the coastline of the former island" (204). Subsidence seems to 

 be excluded; for, "provided that one believes in the permanence of the 

 deep ocean basins, it is clear that Aolcanoes situated on their floors, after 



