LAGOON DEPOSITS. 



I. GENERAL ACCOUNT. 

 By J. Stanley Gardiner, M.A. 



II. REPORT ON CERTAIN DEPOSITS. 



By Sir John Murray, K.C.B., F.R.S. 



(With Plate XXXIV.) 



I. GENERAL ACCOUNT (by J. Stanley Gardiner)'. 



In Appendix A, Section II. of my article on " The Maldive and Laccadive Groups " 

 (vol. I. pp. 317 — 323), I have already refeiTed to some of the deposits found in the atolls 

 and on the banks which we visited. I am greatly indebted to Sir John Murray for kindly 

 examining and giving me the accompanying Re^jort on certain deposits from the lagoons of 

 the atolls which I submitted to him. Perhaps the Section above referred to should be read 

 a second time in connection with this Report, though the latter does not, so far as I can 

 see, invalidate any conclusions therein expressed as to the formation of lagoons, but on the 

 contrary lends them additional important support. 



On the most open banks, such as Miladumadulu and North Mahlos, we found, generally 

 speaking, either a hard bottom without any deposit or else a deposit formed by very coarse 

 broken coral and shell fragments, leaves of Halimeda and allied algae, together with a few 

 bottom-living Foraminifera of large size. As might have been expected, there did not appear 

 to have been anywhere a deposit of any thickness except to leeward of certain reefs, where 

 it might have the characters of nos. 11 and 12 of Sir John Murray's Rejjort. 



Within shallow atolls, or banks which had assumed the atoll shape, the bottom, except 

 along the lines of the currents, was commonly covered by a deposit of white sand. This 

 was always quite loose and never coherent in any way. It consisted of fine fragments of 

 the same materials as on the more open banks, all more or less rounded or smoothed. Except 

 that the remains of pelagic organisms were rarer, the deposit was the same as that which 

 formed the sand of the lagoon-ward parts of the islands (nos. 14 and 15). The grains varied 

 in size, being in enclosed situations extremely small, such as the centre of Minikoi (no. 16), 

 except for leaves of Halimeda and broken shells. In this position no doubt a great part 

 of the deposit was formed by the washings off the land, but that from the velu (lagoon) 

 of Bodu Faro, North Mahlos, a quite open faro (atollon) 13 fathoms in depth, approaches 

 rather to a mud (no. 13). Nos. 17 — 19 are also examples of coral sands from the neighbour- 

 hood of passages into the lagoon of Suvadiva, where currents of greater or lesser force are felt. 



' Sir John Murray suggested that I should give some possess. Consequently, I alone am responsible for any 

 general account of these deposits, as I necessarily had a statements or opinions contained in this Section. 

 local knowledge of the region, which he did not himself 



