[ 394 J 
XXXVII. On the Formation of Iflands . By 
Alexander Dairy mple, Efquire. Com- 
municated by C. Morton, M. D. S, R. S, 
Received May 4, 1 767. 
Read July 2 ■ SHERE is not a part of natural 
! ? 6/ ‘ hiftory more curious, or perhaps to 
a navigator more ufeful, than an enquiry into the 
formation of iflands. The origin of iflands, in ge- 
neral, is not the point to be difcuffed ; but of 
low, flat, iflands in the wide ocean ; fuch as are 
mod of thofe hitherto difcovered in the vaft South- 
fea. 
Thefe iflands are generally long, and narrow; 
they are formed by a narrow bar of land, inclofing 
the fea within it ; generally, perhaps always, with 
fome channel of ingrefs at leafl: to the tide; com- 
monly, with an opening capable of receiving a 
canoe; and frequently fufficient to admit even larger 
veflels. 
The origin of thefe iflands will explain their na- 
ture. What led me firft to this deduction was an 
obfervation of Abdul Roobin, a Sooloo pilot ; that 
all the iflands, lying off the N.E. coaft of Borneo, 
had fhoals to the eaftward of them. 
Thefe iflands being covered to the weftwrard by 
Borneo; the winds from that quarter do not attack 
them 
