da PEOPLES OF THE PHILIPPINES 
While some of these idioms, such as Tagalog, are very 
well known, there is no information on others beyond 
brief vocabularies, and in regard to several dialects 
nothing at all has been published. The classification is 
therefore tentative; but in its main outlines it promises 
to stand. Its most significant feature, well brought 
out by the map, is the tendency toward specialization 
and diversification in the north of the archipelago. 
Three of the five groups of tongues are confined to the 
northern half of the island of Luzon: and as for the 
remaining two, it is not even certain that they are 
distinct. ‘Topography may be responsible. The central 
cordillera of Luzon, in whose region the Northeastern 
and Northwestern groups adjoin and from which Pam- 
pangan is not far removed, is easily the most intricate 
and irregular mountain system in the Philippines, in 
which trade is restricted and communication painfully 
slow even today. Nature has thus provided unusual 
opportunity for local dialects to spring up and become 
accentuated. 
It is clear in every way that intercourse within the 
archipelago occurred much more readily by sea than by 
land even at an early period. A striking example is 
furnished by the Bisayan dialects, whose areas are 
outlined in Map 5. Different dialects are spoken on 
the two sides of single islands of no great size; whereas 
a single dialect extends across straits or seas to the con- 
fronting shores of other islands. The distribution of 
Tagalog and Bisaya on Mindoro points to the same 
condition. Only Ilokano seems to reflect a different 
story, but this tongue had no other islands opposed to 
its original seat of development, and therefore appears 
to have sidled along the coasts of northern Luzon until 
it could spread no farther, and then to have pushed up 
two or three large open river systems during the last 

