chap, i.] PHYSICAL GEOGRAPHY. 23 



of them may never have been actually joined to it. This 

 continent must have been broken up not only before the 

 Western Islands were separated from Asia, but probably 

 before the extreme south-eastern portion of Asia was 

 raised above the waters of the ocean ; for a great part of 

 the land of Borneo and Java is known to be geologically 

 of quite recent formation, while the very great difference 

 of species, and in many cases of genera also, between the 

 productions of the Eastern Malay Islands and Australia, 

 as well as the great depth of the sea now separating them, 

 all point to a comparatively long period of isolation. 



It is interesting to observe among the islands them- 

 selves, how a shallow sea always intimates a recent land- 

 connexion. Tbe Aru Islands, Mysol, and Waigiou, as 

 well as Jobie, agree with New Guinea in their species of 

 mammalia and birds much more closely than they do with 

 the Moluccas, and we find that they are all united to New 

 Guinea by a shallow sea. In fact, the 100-fathom line 

 round New Guinea marks out accurately the range of the 

 true Paradise birds. 



It is further to be noted — and this is a very interesting 

 point in connexion with theories of the dependence of 

 special forms of life on external conditions — that this 

 division of the Archipelago into two regions characterised 

 by a striking diversity in their natural productions, does 

 not in any way correspond to the main physical or 



