304 



The Philippine Journal of Science 



almost aphanitic phase of diorite, succeeding 

 the granite on the east as far as the town 

 of Barlig, where steeply dipping sandy 

 shales are encountered. These incline to 

 the southeast. 



Sandstone makes up the main mass of 

 Mount Amuyao, and from there east to Ca- 

 gayan Valley sediments occur. In places, 

 as at Natonin, there are small areas of 

 extrusive rocks overlying the Tertiary 



j sediments. 



3 



8 A comparison of -the radioactivity 



| of the waters of the mountains of 

 | northern Luzon and that of the 

 | waters examined in the Luzon low- 

 s lands indicates that the typical 

 I lowland waters show the higher 

 " radioactivity. The highest radio- 

 s activity (1325 X 10- 12 ) determined 

 I in the mountains (Adukpung spring, 

 | Kiangan) was practically identical 

 I with that (1300 X 10- 12 ) of the 

 § most active lowland spring (Sinabac 

 | spring, Majayjay, Laguna), but con- 

 l siderably less than that (2100 X 

 I 10- 1 -) of the most active lowland 

 g water (from a flowing well in Batan- 

 I gas, Batangas). 



I In Nueva Vizcaya the radioactivity 

 | encountered was uniformly low, so 

 * that the present work has served to 

 | emphasize the peculiarity noted last 

 § year, that is, a low radioactivity in 

 c all waters except those in a smajl 

 ci district in Ifugao. Since the waters 

 g studied varied greatly, both in chem- 

 ical quality and in the geological 

 formations from which they were 

 obtained, and since those highly 

 radioactive showed no apparent pe- 

 culiarities or marked differences 

 from other, less active waters, the 

 high activity of the Ifugao waters 

 seems to be due to isolated local 

 deposits of radioactive material. 



