376 PEECY SLADEN TEUST EXPEDITION. 



gasteropods, Cliona borings, and Lithothamnion " *. It is further stated that the bottom 

 of the core " is composed of Poraminif era and detrital material cemented by crystalline 

 dolomite " f- 



These materials are such as are found off coral-reefs in depths of 100 to 250 fathoms, 

 and the genera of Foramiuifera are those found in most of the lists of Eoraminifera 

 occurring in the deposits around Bermuda, Fiji, Tongatabu, &c., published in the 

 ' Challenger ' Reports : Summary of Results. 



It therefore seems most reasonable to conclude that the bottom of the boring repre- 

 sents the sea-floor at a former time, which has been covered up by the material torn 

 from the reef, thus forming a talus for the seaward growth of the reef to its present 

 jiosition. Since that time it seems probable that the growing face of the reef has pro- 

 ressed in a seaward direction a distance of 300 or 400 yards, judging from present-day 

 conditions. For instance, of the soundings taken by Captain Field around Funafuti 

 Atoll in 1897, one is shown off the eastern edge of the reef at the island of Funafuti in 

 163 fathoms about 400 yards distant ; farther south a sounding in 193 fathoms is shown 

 about 340 yards from the edge of the reef ; off the western side of the reef a sounding in 

 175 fathoms, and off the northern side a sounding in 167 fathoms, are shown at similar 

 distances from the reef. Roughly speaking, then, it may be said that a depth of 

 1114 feet occurs about 350 to 400 yards from the edge of the reef, giving an average 

 gradient of the seaward face of the reef of 1 in 1, equal to a slope of 45°. The relative 

 position of the bore to the former and present position of the reef may be roughly 

 indicated, as in the accompanying diagram drawn to scale (p. 375). 



3 



DESCRIPTIONS OF THE DEPOSIT-SAMPLES 

 COLLECTED BY Mr. J. STANLEY GARDINER IN THE INDIAN OCEAN IN 1905. 



The samples received from Mr. Gardiner number 79, but of these 34 are either too 

 meagre in amount to admit of description, or apparently do not represent the deposit at 

 the bottom, and are therefore not fully described, so that only 45 samples have been 

 submitted to detailed examination and description. 



Of the described samples, 17 were taken in the open sea in depths ranging from 

 1822 to 2438 fathoms, 21 in the vicinity of Chagos in depths ranging from 432 to 

 2100 fathoms, 3 from the neighbourhood of Mauritius from depths of 500 to 818 fathoms, 



* ' The Atoll of Fuuafuti : Keport of the Coral-Keef Committee of the Royal Society,' p. 294 (London, 1904). 

 t Op. cit. p. 296. 



