Indo-Malay Islands. 155 



new land, being a great alluvial swamp formed by torrents 

 from the mountains a hundred miles distant. Banca, on the 

 other hand, agrees with Malacca, Singapore, and the inter- 

 vening island of Lingen, in being formed of granite and lat- 

 erite ; and these have all most likely once formed an exten- 

 sion of the Malay Peninsula, As the rivers of Borneo and 

 Sumatra have been for ages filling up the intervening sea, we 

 may be sure that its depth has recently been greater, and it 

 is very probable that those large islands were never directly 

 connected with each other except through the Malay Penin- 

 sula, At that period the same species of squirrel and Pitta 

 may have inhabited all these countries ; but when the subter- 

 ranean disturbances occurred which led to the elevation of 

 the volcanoes of Sumatra, the small island of Banca may 

 have been separated first, and its productions being thus iso- 

 lated, might be gradually modified before the sej^aration of 

 the larger islands had been completed. As the southern 

 part of Sumatra extended eastward and formed the narrow 

 straits of Banca, many birds and insects and some Mammalia 

 would cross from one to the other, and thus produce a general 

 similarity of productions, while a few of the older inhabit- 

 ants remained, to reveal by their distinct forms their difier- 

 ent origin. Unless we suppose some such changes in physical 

 geography to have occurred, the presence of peculiar species 

 of birds and mammals in such an island as Banca is a hope- 

 less puzzle ; and I think I have shown that the changes re- 

 quired are by no means so improbable as a mere glance at 

 the map would lead us to suppose. 



For our next example, let us take the great islands of 

 Sumatra and Java. These approach so closely together, 

 and the chain of volcanoes that runs through them gives 

 such an air of unity to the two, that the idea of their having 

 been recently dissevered is immediately suggested. The na- 

 tives of Java, hoAvever, go further than this ; for they actu- 

 ally have a tradition of the catastrophe which broke them 

 asunder, and fix its date at not much more than a thousand 

 years ago. It becomes interesting, therefore, to see what sup- 

 port is given to this view by the comparison of their animal 

 productions. 



The Mammalia have not been collected with sufiicient 



