CHAP. XXXIII.] PHYSICAL GEOGRAPHY. 289 



straits of irregular width and depth, but not the river-like 

 channels which actually exist. If, again, we suppose the 

 last movement to have been one of subsidence, reducing 

 the size of the islands, these channels are quite as inex- 

 plicable ; for subsidence would necessarily lead to the 

 flooding of all low tracts on the banks of the old rivers, 

 and thus obliterate their courses; whereas these remain 

 perfect, and of nearly uniform width from end to end. 



!N"ow if these channels have ever been rivers they must 

 have flowed from some higher regions, and this must have 

 been to the east, because on the north and west the sea- 

 bottom sinks down at a short distance from the shore to an 

 unfathomable depth; whereas on the east a shallow sea. 

 nowhere exceeding fifty fathoms, extends quite across to 

 ]!»rew Guinea, a distance of about a hundred and fifty miles. 

 An elevation of only three hundred feet would convert the 

 whole of this sea into moderately high land, and make 

 the Aru Islands a portion of ISTew Guinea ; and the rivers 

 which have their mouths at Utanata and "Wamuka, might 

 then have flowed on across Aru, in the channels which are 

 now occupied by salt water. When the intervening land 

 sunk down, we must suppose the land that now constitutes 

 Aru to have remained nearly stationary, a not very impro- 

 bable supposition, vv'hen we consider the great extent of 

 the shallow sea, and the very small amount of depression 

 the land need have undergone to produce it. 

 VOL. II. u 



