252 The Philippine Journal of Science i9i6 



plying between Bulan and Irosin, taking in rice, fish, and other 

 supplies, and returning with hemp and copra for Manila. 



The road to Irosin follows a general northeast course, crossing 

 first about 8 kilometers of coastal plain deposits, and then 

 by a series of grades it winds up over the divide and dovni 

 into Irosin Valley. The divide consists of a chain of andesitic 

 and basaltic hills trending northwest-southeast and forming the 

 western limit of what Adams and Pratt - have designated as 

 the third division of the Southeastern Cordillera of Luzon. 



IROSIN 



Irosin, including its barrios, is said to have about 12,000 

 people. It is situated at the foot of Mount Bulusan and forms 

 a semicircle around the base. Aneroid readings place its eleva- 

 tion at from 50 to 60 meters above sea level. Being almost 

 surrounded by mountains, it is well protected from baguios, 

 although during the recent rainy season (November to Feb- 

 ruary) floods occurred which carried out most of the bridges 

 and caused much damage to the roads. 



Arriving in Irosin in the afternoon of the 28th, I could see no 

 confusion, and except for a small amount of fine volcanic ash 

 in sheltered places, there were no remnants of the eruption. As 

 th.e summit of the mountain was surrounded by heavy clouds, it 

 was not possible to tell whether or not activity had entirely 

 ceased. 



1916 ERUPTION 



I obtained much of the data concerning the events of the 

 eruption from Mr. S. B. Chestnut, district school supervisor, 

 who was in Irosin during part of the eruption. His information 

 was supplemented by that of two Filipino school-teachers and 

 the municipal officers. Older residents of Irosin remember the 

 eruptions of 1886 and 1894, but very little reliable information 

 could be obtained. 



On Tuesday, January 18, about 2 o'clock in the morning, rice 

 planters heard a faint noise, felt a slight quake, and then noticed 

 "smoke" issuing from the volcano which settled into the valley. 

 Ashes began to fall. No incandescence could be seen from 

 Irosin, but people in Mombon, a barrio about 3 kilometers north- 

 west of Irosin, claim to have seen "fire." Most of the ashes 

 fell shortly after the initial eruption, then a small amount fell for 

 a period of three days. All together Irosin received about 1 



'Adams, G. I., and Pratt, W. E., Phil. Journ. Scl, Sec. A (1911), 6, 

 455. 



