244 



AUSTRALASIA. 



natives not even approximate estimates are available. Nevertheless tlie present 

 population may be fixed at not less than seven millions, or more than nine 

 millions, in a total area of about 118,000 square miles. 



Although forming a group quite distinct from Indonesia, from which they are 

 separated by two marine abysses, one nearly two thousand five hundred, the other 



over two thousand five hun- 



Fig. 106. — The three Isthmuses of Indonesia and the 

 Philippines. 



Scale 1 : 18,000,000. 



dred fathoms deep, the Philip- 

 pines are connected with the 

 southern lands by three long 

 ridges, partly rising above 

 the surface, partly covered 

 by shallow water. Of these 

 three isthmuses the north- 

 western is the most regular 

 and best developed, being 

 constituted for over half its 

 extent by the long narrow 

 island of Paragua. Between 

 Mindoro and the north-west 

 point of Borneo the deepest 

 parts of the sill limited by 

 Balabac and Bangney do not 

 average more than tweoty- 

 five fathoms. Balabac Strait 

 between Paragua and Borneo 

 is occupied by reefs resem- 

 bling in outline the alluvial 

 islands of a delta, and formed 

 under the influence of the 

 marine current which, during 

 the south-west monsoon, sets 

 strongly towards the Sulu Sea. 

 The second isthmus is formed 

 by the Sulu Archipelago, 

 which connects the north-east 

 point of Borneo with the 

 western extremity of Min- 

 danao. But here the shallow 

 channel, through which the 

 deep waters of the Sulu Sea communicate with the still deeper Celebes Sea, is 

 traversed by a system of alternating currents over two hundred and fifty fathoms 

 in depth. Lastly, east of the nearly circular trough of the Celebes Sea the penin- 

 sula of Minahassa, with the Sanguir Archipelago and other islands, develop a third 

 isthmus sweeping round to the southernmost point of Mindanao. This connecting 



Depths. 



1 



to 1,000 

 Fathoms. 



1,000 to 2.000 

 Fathoms. 



2,000 Fathoms 

 and upwards. 



300 Miles. 



